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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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$ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon .
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pm why is it that phenolphthalein is soluble in ethanol but not soluble in water though both ethanol and water are polar ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done !
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of -2 , but cl is more electronegative than o right ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions .
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so cl should have an oxidation number with a negative sign right ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step .
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how would i balance the charges on a half-reaction if the charges on either side are zero ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ?
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what is being oxidized and reduced in the following equation and why ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent .
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2fe2o3 why is the oxidation number of 2fe2 +3 ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions .
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if there is no reaction such copper added to hydrochloric acid , would there be gas formation ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal .
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if there was no gas formation would n't the reactant stay the same meaning that there is no equation as well , right ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced .
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in the disproportionation reactions example , why did the oxidation number increased from +1 to +5 when it oxidized by oxygen ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound .
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why is the oxidation number of oxygen -2 when the previous article ( oxidation numbers ) states that oxygen is positive when in a binary compound with flourine ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction .
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how is the cl oxidation number equal to 1+ in 3clo- ?
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what is a redox reaction ? a redox ( or oxidation-reduction ) reaction is a type of chemical reaction that involves a transfer of electrons between two species . we can tell there has been a transfer of electrons if there is any change in the oxidation number between the reactants and the products . redox reactions are everywhere ! your body uses redox reactions to convert food and oxygen to energy plus water and $ \text { co } _2 $ , which we then exhale . the batteries in your electronics also rely on redox reactions , which you will hear more about when we learn electrochemistry . can you find other examples of redox reactions happening around you ? an example and important terms redox reactions have some associated terms you should be comfortable using . we will go over these terms using the following example reaction : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ here are some questions we want to be able to answer : $ 1.~ $ is this reaction a redox reaction , and how do we know ? $ 2.~ $ if this is a redox reaction , what is being reduced and oxidized ? $ 3.~ $ what is the reducing agent in this reaction ? $ 4.~ $ what is the oxidizing agent in this reaction ? question $ 1 $ : based on the title of this article , we can make an educated guess about the first part of this question . yes , this is probably a redox reaction , but how do we know that for sure ? we need to show there is an electron transfer occurring , and we can do that by checking if any oxidation numbers change from the reactants to the products . if we find the oxidation numbers for each atom in the reactants and products , we get the following : $ 2 \text { fe } _2 \text o_3 ( s ) + 3 \text c ( s ) \rightarrow 4 \text { fe } ( s ) + 3 \text { co } _2 ( g ) $ $ \purplec { ~~~\downarrow~~~~\downarrow ~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~~~\downarrow~~~~~~~~~~~~~\downarrow~~~\downarrow } ~~~~~~~~~ $ $ \purplec { +3 , -2~~~~~~~~~~~~~0~~~~~~~~~~~~~~~0~~~~~~~~+4 , -2 } ~~~~~~~~~\text { ( oxidation numbers ) } $ we can use the oxidation numbers to answer the second part of question $ 1 $ , because we can show that the oxidation numbers for carbon and iron are changing during the reaction from a transfer of electrons . question $ 2 $ : carbon being oxidized because it is losing electrons as the oxidation number increases from $ 0 $ to $ +4 $ . iron is being reduced because it is gaining electrons when the oxidation number decreases from $ +3 $ to $ 0 $ . question $ 3 $ : the reducing agent is the reactant that is being oxidized ( and thus causing something else to be reduced ) , so $ \text c ( s ) $ is the reducing agent . question $ 4 $ : the oxidizing agent is reactant that is being reduced ( and thus causing something else to be oxidized ) , so $ \text { fe } _2 \text o_3 ( s ) $ is the oxidizing agent . common types of redox reactions since redox reactions are an important class of reactions , we want to be able to recognize them . there are a few special types of redox reactions you might want to be familiar with . for each of these examples , take a minute to figure out what is getting reduced and oxidized ! $ 1.~ $ combustion reactions a combustion reaction is a redox reaction between a compound and molecular oxygen ( $ \text o_2 $ ) to form oxygen-containing products . when one of the reactants is a hydrocarbon , the products include carbon dioxide and water . the following reaction is the combustion of octane , a hydrocarbon . octane is a component of gasoline , and this combustion reaction occurs in the engine of most cars : $ 2\text c_8 \text h_ { 18 } + 25 \text o_2 \rightarrow 16 \text { co } _2 ( g ) + 18\text h_2 \text o $ $ 2.~ $ disproportionation reactions a disproportionation reaction ( or auto-oxidation reaction ) is a reaction in which a single reactant is both oxidized and reduced . the following reaction is for the disproportionation of hypochlorite , $ \text { clo } ^- $ : $ 3\text { clo } ^- ( aq ) \rightarrow \text { clo } _3^- ( aq ) + 2\text { cl } ^- ( aq ) $ if we analyze the oxidation numbers for chlorine , we see that the reactant $ \text { clo } ^- $ is being oxidized to $ \text { clo } _3^- $ ( where the oxidation number increases from $ +1 $ to $ +5 $ ) . at the same time , the chlorine in some other molecules of $ \text { clo } ^- $ are being reduced to $ \text { cl } ^- $ ( where the oxidation number decreases from $ +1 $ to $ -1 $ ) . oxygen has an oxidation number of $ -2 $ in both $ \text { clo } ^- $ and $ \text { clo } _3^- $ , so it does not get oxidized or reduced in the reaction . $ 3.~ $ single replacement reactions a single replacement reaction ( or single displacement reaction ) involves two elements trading places within a compound . for example , many metals react with dilute acids to form salts and hydrogen gas . the following reaction shows zinc replacing hydrogen in the single replacement reaction between zinc metal and aqueous hydrochloric acid : $ \text { zn } ( s ) +2\text { hcl } ( aq ) \rightarrow \text { zncl } _2 ( aq ) +\text h_2 ( g ) $ balancing a simple redox reaction using the half-reaction method redox reactions can be split into reduction and oxidation half-reactions . chemists use half-reactions to make it easier to see the electron transfer , and it also helps when balancing redox reactions . let 's write the half-reactions for another example reaction : $ \text { al } ( s ) + \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { al } ^ { 3+ } ( aq ) + \text { cu } ( s ) $ is the above reaction balanced ? our atoms appear to be balanced : we have $ 1\ , \text { al } $ atom and $ 1\ , \text { cu } $ atom on each side of the arrow . however , when we add up the charges on the reactant side we get a $ 2+ $ charge , which is not the same as the $ 3+ $ charge on the product side . we need to make sure both the atoms and the charges are balanced ! we will use the half-reaction method to balance the reaction . reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side . we can balance the charges by including the electrons being transferred , and then we will get our reduction half-reaction : $ \text { cu } ^ { 2+ } ( aq ) +2e^-\rightarrow \text { cu } ( s ) ~~~~~~~~~~~~~~~~~~\blued { \text { reduction half-reaction } } $ the balanced half-reaction tells us that $ \text { cu } ^ { 2+ } $ is gaining $ 2 e^- $ per copper atom to form $ \text { cu } ^0 $ . so where are those electrons coming from ? we can follow the trail of electrons to the oxidation half-reaction . oxidation half-reaction : the oxidation half-reaction shows the reactants and products participating in the oxidation step . this reaction will include the oxidation of $ \text { al } ( s ) $ to $ \text { al } ^ { 3+ } $ , and we will also want to make sure the half-reaction is charge-balanced : $ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) +3e^-~~~~~~~~~~~~~~~~~~~\blued { \text { oxidation half-reaction } } $ the oxidation half reaction tells us that each atom of $ \text { al } ( s ) $ is losing $ 3e^- $ to form $ \text { al } ^ { 3+ } $ . we will combine the balanced half-reactions to get the balanced overall equation , but there is one more thing to check . the electrons must cancel out in the overall equation . another way to think of this that we want to make sure that any electrons that are released in the oxidation half-reaction get used up in the reduction half-reaction . otherwise we would have stray electrons floating around ! that means we need the number of electrons being transferred in each half-reaction to be equal . we can multiply the reduction half-reaction by $ 3 $ and multiply the oxidation half-reaction by $ 2 $ so both reactions involve the transfer of $ 6 $ electrons : $ \redd { 3 } \times [ \text { cu } ^ { 2+ } ( aq ) + { 2e^- } \rightarrow \text { cu } ( s ) ] ~~~~~~~~~~~~~~~~~~~3 \times \text { reduction half-reaction } \ \greend { 2 } \times [ \text { al } ( s ) \rightarrow \text { al } ^ { 3+ } ( aq ) + { 3e^- } ] ~~~~~~~~~~~~~~~~~~~~~2 \times \text { oxidation half-reaction } $ now that we have the same number of electrons in each half-reaction , we can add them together to get our overall balanced equation : $ \begin { align } \cancel { 6e^- } +\redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow ~~~~~~~~~~~~~~~~~~~~~~\redd { 3 } \text { cu } ( s ) ~~~~~~3 \times \text { reduction half-reaction } \ \\greend { 2 } \text { al } ( s ) ~~~~~~~~~~~~~~~~~~~~~~~ & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) +\cancel { 6e^- } ~~~~~~~~~2 \times \text { oxidation half-reaction } \ \\hline \greend { 2 } \text { al } ( s ) + \redd { 3 } \text { cu } ^ { 2+ } ( aq ) & amp ; \rightarrow \greend { 2 } \text { al } ^ { 3+ } ( aq ) + \redd { 3 } \text { cu } ( s ) ~~~~~~~~\text { overall balanced reaction } \end { align } $ lastly , we can check to see if any reactants and products appear on both sides . since that is not the case here , we are done ! our reaction is balanced for both mass and charge . summary we can identify redox reactions by checking for changes in oxidation number . redox reactions can be split into oxidation and reduction half-reactions . we can use the half-reaction method to balance redox reactions , which requires that both mass and charge are balanced . three common types of redox reactions are combustion , disproportionation , and single replacement reactions . try it !
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reduction half-reaction : the reduction half-reaction shows the reactants and products participating in the reduction step . since $ \text { cu } ^ { 2+ } $ is being reduced to $ \text { cu } ( s ) $ , we might start by writing out that step : $ \text { cu } ^ { 2+ } ( aq ) \rightarrow \text { cu } ( s ) $ however , this is not the correct half-reaction , because it is not charge-balanced . there is a net charge of $ 2+ $ on the reactant side and $ 0 $ on the product side .
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is option b is correct ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ?
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will there be questions that are a higher level than level 4 ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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how do i send my sat date to get my practice stuff designed according to how much time i have left till the day i take my sat ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ?
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what level at school do i got be to take the test ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there .
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when would be the ideal time for me take the sat in order to be admitted to ivy league schools ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 .
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once the scores from psat test have been linked from the college board site , does khan set up a group of activities based on scores to assist practice/needs ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ?
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is there a way to toggle scratchpad on sat math practice areas ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat .
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is there a limited amount of sat practice on my account , in terms of questions/passages ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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my test is january 14 , and i just started studying today , so could anyone also please include a study schedule so i can still get a high score ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed .
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i would like to know how long would it take to complete these series of quizzes so that he can take the sat practice test ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there .
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what is the length of time frame for taking the sat practice exam ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible .
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does the whole exam need to be taken in one sitting or can it be broken down into parts ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ?
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what do the different shades of blue mean on the wifi-looking symbol on the list of math skills i can practice ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ?
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can we get score estimates based on our skill level/progress ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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can someone help me understand what it is graded out of and what is a good score ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed .
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how much time does it take to take the practice sat test ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions .
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if i take the pdf version of a practice sat test , will it be marked as a completion on my activity tab ( schedule ) ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat .
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is the official sat practice test day going to be at a specific time ( where everyone takes it at the same time like a real sat ) or is it a reminder day to practice for the sat ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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in the sat , would my different method of solving the equation affect my score ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat .
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greetings , i am a homeschool striving to study for the sat and i wanted to know anyone else is doing to accompanying the aid of khan academy with any mentoring for a low budget income student besides kaplan ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' .
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my mean if i want to take the test pm in china ( gmt +8 ) , then do i need to schedule am ( gmt -5 ) ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ?
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do i need to log in in order to use the revision assistant for the sat essay practice ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat .
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how do i sign up for the sat question of the day ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words .
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i 've taken a psat test before with a different company than college board , is there a way i could upload the results ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ?
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what do the shades and boxes in the semi circle mean ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly .
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hi , for the essay , would marks be deducted for spelling ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ?
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how do i link my psat/nmsqt scores without a college board account ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper .
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why isnt there an essay section in your individual practise section ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet .
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when will more practice tests be uploaded ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ?
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are the articles and reading materials on another level of difficulty and the questions level four , or are the articles the same difficulty as the level 3 or 2 with questions varying in difficulty ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat .
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should the sat i and sat ii score be sent to the university at the same time ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ?
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is it possible to take the practice sat tests over multiple days , or do you have to do it all in one day ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ?
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are the diagnosed skill levels based off the psat most recently taken ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores .
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how can i connect my psat scores to my collegeboard account ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat .
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i am 10th grade i am planing on taking the sat next year in 11th grade , i just wanted to know is study during summer break enough or should i start now ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed .
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i 'm supposed to take my sat today on khan academy , but there does not seem to be a button allowing my to take my exam , it simply says `` review tips for test day '' do i have to go some place locally available to take it ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat .
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after i have set up a class specifically for sat prep and my student has enabled sharing , how do i access the sat class tab ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat .
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how many times you can take the sat test for free ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ?
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i am getting level 3 , and 4 questions , and constantly get them wrong t the rate of 2 out of 11. how do i move down a level to wok my way up ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores .
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how to earn psat 8/9 earth badge ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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the ipone app did not score my test correctly ( see my chart ) i was able to get it to rescan - but the old scores are there and messing up the recomendations - how do i delete practice tests which are scored incorrectly ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed .
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how can i know the exact date of when i will take my psat exam so i can set up my practicing schedule ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ?
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some of skills are preceded by a light purple logo and others have a dark purple logo , what does this mean ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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when does my sat score show up ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us !
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is there a certificate of completion , or other document of equivalence , issued at the end of this course ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet .
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are the practice tests made to be more around the current levels you 're working on , or did i just do really bad ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience .
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which part of your excellent website can i use to find lessons and solved examples relating to the topics included in math sat 2016 ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ?
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my question is : on the psats and sats , are the passages chosen on random from any skill level , that is , from simple to more complex ; does this also apply to the questions associated with those passages ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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are there any choices in the sat exam which comprises of maths , reading , writing and an essay , and if yes then how much questions can we afford to leave while still being able to score hundred percent score ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ?
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do we have solutions for each question to know our mistakes ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ?
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if i had reach all the portions level 4 , what does that means ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ?
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i mean do we have to learn to convert from feet to inches to yards and so on ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us !
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how was the 225 computated ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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the practice tests state that 24 correct answers is a score of 500 , while college board materials my students have received state that 26 correct answers is a 500 ... which is correct ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us !
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does khan academy offer an opportunity to take practice tests in a real life testing center situation near you instead of online ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores .
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and does anyone really take advantage of these opportunities ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update .
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how do i calculate my test score from the college board book diagnostic tests ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed .
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do you have to take the saturday practice tests 0 , or can you take them anytime of the day ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ?
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how do i make the personalized practice based upon my sat score and not my psat score ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat .
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how do i change my amount of questions i would like to receive for my daily practice for sat ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed .
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is there a way i could take them down and just do a diagnostic exam to see where i 'm at currently ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly .
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how do i answer the questions on the sat , i mean do i need to circle the right choice or to remove the wrong choices , or they 'll give us an answer paper sheet where we need to fill in the blanks ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results .
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how do you change the email for who reminders are sent to ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet .
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i 'm taking the sat without the essay- can i set my practice so it does n't make me practice writing ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly .
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is there a way to see a predicted sat score based on how i have done on the questions ?
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check out our answers to folks ' frequently asked questions . if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better . top questions q : my psat/nmsqt® scores are n't showing up , but i already connected my account to college board . what can i do ? a : here are the steps you should take to straighten this out : 1 . log in to collegeboard.org and check that you can see your psat/nmsqt® or psat 8/9 scores . we 're not able to read in psat/nmsqt® scores from 2014 or earlier or 2400-point-scale sat scores . 2 . if you can see your scores on collegeboard.org , visit your khan academy settings and click `` disconnect from college board '' . 3 . the button will change to '' connect to college board '' – click it . you will be prompted again to send your exam results . once that 's complete , your 2015 psat/nmsqt® scores should now be visible . q : i ’ m a teacher or parent – how can i follow my students ’ progress ? a : we don ’ t have a way for teachers and coaches to view their students ’ progress in official sat practice . we are planning to add ways for both students and their coaches to view their progress . q : why isn ’ t the activity tab in my profile showing my sat practice activity ? a : we ’ re working on making your sat practice activity show up there and also planning to add a place to view your progress and review your answers to practice questions . am i in the right place ? q : i need to practice for the psat/nmsqt® or psat 8/9 ; where should i go ? a : for the psat/nmsqt® , you can practice right here ! the psat/nmsqt® has the same content as the sat but minus the hardest questions and the essay . you can also download a psat/nmsqt® practice exam to take on paper . the psat 8/9 has the same structure as well but with even more hard sat content removed . official practice for the sat may contain too much of the harder content to be really useful for you , but you are welcome to try out practicing with us . skill levels and practice questions q : i ’ ve answered all the level 4 ( most challenging ) questions for a skill but i 'd still like to keep practicing . is there a way i can practice the questions from the other levels ? a : we don ’ t currently have a way for you to switch to questions from an earlier level without your intentionally missing questions to drop your level down . we are working to create more questions in general . q : the system started me at level 2 , easier , but i ’ m ready for level 3 or 4 . can i skip ahead to those questions ? a : we don ’ t currently have a way for you to instantly switch what level of questions you are working on . q : i ran into a mistake on a question . how can i let you know it needs to be fixed ? a : when you encounter a mistake on a question , you should click the “ report a mistake ” link in the footer of the page where you see that question , and let us know what the mistake is . q : is there a way for me to tell the system that for a particular question , i ’ m just guessing ? i guessed , got some right , and went up a level , but now the questions it ’ s giving me are too hard . a : in the diagnostic quizzes , you can tell the system you ’ re guessing , but you ’ re right , you can ’ t currently do that in other places . this is on our list of things to add . q : what do the different skill levels mean ? do they map to the mastery levels in regular khan academy math ? a : the skill levels are different than the regular khan academy math mastery system levels . for sat , higher levels contain harder questions . you will also move up or down through the levels depending on how many questions you answer correctly . diagnostics and practice exams q : when i first did my diagnostic quizzes , i was just checking it out and not really trying . can i redo those quizzes so i can get more accurate starting levels ? a : sorry , there ’ s not a way to reset your diagnostic quizzes—though you can reset practice exams . once your psat/nmsqt® results become available , however , you will be able to connect those to your account and increase your skill levels based on how you did . q : can i print out your practice exams and automatically upload my answers to the system ? a : you can download the practice exams , but to upload your results into our system and get new recommendations , you will need to enter the answers from your answer sheet into the regular online practice exam . you can use the college board ’ s sat practice app to take a picture of your paper exam sheet and get the score . those results are not currently shared with khan academy , though , so your recommendations and levels will not update . q : i took a full practice exam , but the system still wants me to complete the diagnostic quizzes . can ’ t the system just use my practice exam to set my starting levels and practice recommendations ? a : we agree this would be more efficient , but we haven ’ t built this into the system yet . once the oct 2015 psat/nmsqt® results are released , you will be able to connect your actual psat/nmsqt® results in lieu of taking the diagnostic quizzes . q : on the reading and writing and language tests , i 'm having trouble seeing commas and semicolons below underlined words . is this formatting identical to what i will see on the actual sat ? a : on the practice and diagnostic tests , it can be tricky to discern whether you are looking at an underlined comma , semicolon , period , or colon . these punctuation marks will be underlined when they are part of the question being asked . this will not be an issue when you take the sat itself ; the underline will be at a lower placement so you can see the punctuation more clearly . for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat . the college board works closely with khan academy staff at all stages of content creation to ensure that the test questions you see on the khan academy website are the same types of questions you will see on the actual sat . content writers from khan academy collaborate with the writing staff at college board , who revise multiple drafts of their works . other questions q : i accidentally connected my khan academy account to a student 's , or someone else 's , college board account , how do i disconnect it ? a : go to your khan academy settings and click the `` disconnect from collegeboard.org '' button . q : can i watch the sat videos offline ? a : on the page where you watch the video , if you click the “ info ” button , it will open a menu that contains a link to “ download this video ” . also , if you have the khan academy iphone/android app , which does not contain sat practice questions but does have the videos , you can download videos to your phone for offline viewing . q : can i print out all of the practice questions ? a : we don ’ t have plans to do this , though we definitely understand the benefits of being able to practice offline . you can , however , download the practice exams . q : do you have an iphone or android app i can use for sat practice ? a : you can visit khanacademy.org/sat on your mobile web browser to use the practice system ; turn your phone sideways for the best experience . we do not have a dedicated smartphone app for this system , but you may also want to try the college board ’ s sat practice app . q : can i earn badges for doing sat practice like i can when studying other subjects on khan academy ? a : your practice on official sat practice will help you earn some of the points- and video-based badges available on khan academy , but we still need to create specialized badges that apply well to the sat practice system . q : can i use my collegeboard extended time accommodation when practicing for the sat on khan academy ? a : yes , you can visit your khan academy settings and fill in the form there . you will then be able to use the extended time on all full practice tests and timed mini-sections that you take on khan academy . contact us if we still have n't answered your question , contact us ! and always let us know if you have a problem or a sweet idea for making this system better .
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for your practice , you can enlarge your screen view if you ’ re having trouble seeing the punctuation . q : how does khan academy create the official sat practice exams and test questions ? official sat practice on khan academy is a partnership with the college board , the company that creates the sat .
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out of how much are these displayed sat test scores on the full test ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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what does taring a piece of glassware mean ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample .
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so why do we have to take into account the 2 in bacl2.2h2o but not the one in 2h2o ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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$ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ .
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but should n't it be 2 moles of h2o ( g ) for everyone one mole of bacl2 and 2 moles of h2o ( g ) for every 2 moles of h2o from the reactant ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks .
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should n't it be `` having a low ( flat/plane ) surface area will increase the rate of evaporation ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating .
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then , is the mass of kcl equal to 9.51g - 0.37g ( h2o ) - 2.51g ( bacl2'2h2o ) = 6.63g ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass .
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how would you find the gravimetric factor from grams of pcl3 to grams of p ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass .
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how can amu of bacl2 = 247.47 when ba = 137.3 and cl is 35.45*2 ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte .
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can gravimetric analysis be used to determine the identity of an unknown substance ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample .
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what is the difference between limiting reactant and limiting reagent ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry !
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why is n't the mass of water .37 grams or 96.11 % ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ?
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what if igor contaminated a metal hydrate with another metal hydrate or some solution ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ .
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are we assuming that when the sample was contaminated , only kcl was mixed in and no additional amount of water was added ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass .
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in gravimetric analysis of a metal carbonate , what two componds are dissolved in the filtrate after the suction filtration step ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake .
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what could you do to ensure that the crucible and precipitate is dry ?
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass . the chemical we are trying to quantify is sometimes called the analyte . we might use gravimetric analysis to answer questions such as : what is the concentration of the analyte in a solution ? how pure is our sample ? the sample here could be a solid or in solution . there are $ 2 $ common types of gravimetric analysis . both involve changing the phase of the analyte to separate it from the rest of a mixture , resulting in a change in mass . you might hear either or both of these methods being called gravimetric analysis as well as the more descriptive names below . volatilization gravimetry involves separating components of our mixture by heating or chemically decomposing the sample . the heating or chemical decomposition separates out any volatile compounds , which results in a change in mass that we can measure . we will go though a detailed example of volatilization gravimetry in the next section of this article ! precipitation gravimetry uses a precipitation reaction to separate one or more parts of a solution by incorporating it into a solid . the phase change occurs since the analyte starts in the solution phase and then reacts to form a solid precipitate . the solid can be separated from the liquid components by filtration . the mass of the solid can be used to calculate the amount or concentration of the ionic compounds in solution . in this article , we will go through an example of using volatilization gravimetry in a chemistry lab setting . we will also discuss some of the things that might go wrong during a gravimetric analysis experiment and how that might effect our results . example : determining the purity of a metal hydrate mixture using volatilization gravimetry bad news ! we have just been informed by our inept lab assistant , igor , that he may have accidentally contaminated a bottle of the metal hydrate $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ with an unknown amount of $ \text { kcl } $ . in order to find the purity of our $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we heat $ 9.51 \ , \text g $ of the metal hydrate mixture to remove water from the sample . after heating , the sample has a reduced mass of $ 9.14 \ , \text g $ . what is the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original mixture ? gravimetric analysis problems are simply stoichiometry problems with a few extra steps . hopefully you will remember that in order to do any stoichiometric calculations , we need the coefficients from the balanced chemical equation . first let ’ s analyze what is happening when we heat the sample . we are removing water from the $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to form anhydrous $ \text { bacl } _2 ( s ) $ and water vapor , $ \text h_2 \text o ( g ) $ . by the end of our heating process we should be left with a mixture of anhydrous $ \text { bacl } _2 ( s ) $ and $ \text { kcl } ( s ) $ . in the following calculations , we are going to make the following assumptions : all mass lost from the sample is from evaporated $ \text h_2 \text o $ , as opposed to some other decomposition process . all of the water is coming from the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . note : we don ’ t know anything about how much of the contaminant , $ \text { kcl } $ , is in the mixture . it could be anywhere from $ 0-100 \ % \ , \text { kcl } $ by mass ! it probably isn ’ t $ 100\ % \ , \text { kcl } $ though , since we did lose water after heating . we can express the dehydration reaction in terms of a balanced chemical equation : $ \text { bacl } _2 \cdot 2 \text h_2 \text o ( s ) \rightarrow \text { bacl } _2 ( s ) + 2 \text h_2 \text o ( g ) $ based on the above balanced equation , we expect to make $ 2\ , \text { mol h } _2 \text o ( g ) $ for every $ 1 \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ . we will use this stoichiometric relationship in our calculations to convert the moles of water lost to the moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . let 's go through the calculation step-by-step . step $ 1 $ : calculate change in sample mass we can find the amount of water lost during the heating process by calculating the change in mass for our sample . $ \begin { align } \text { mass of } \text h_2 \text o & amp ; = \text { initial sample mass } - \text { final sample mass } \ & amp ; = 9.51\ , \text { g } -9.14\ , \text { g } \ & amp ; =0.37\ , \text { g h } _2 \text o \end { align } $ step $ 2 $ . convert mass of evaporated water to moles in order to convert the amount of water lost to the amount of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio , we will need to convert the mass of evaporated water to moles . we can do this conversion using the molecular weight of water , $ 18.02\ , \text { g/mol } $ . $ \text { mass of water } =0.37\ , \cancel { \text { g h } _2 \text o } \times \dfrac { 1 \ , \text { mol h } _2 \text o } { 18.02\ , \cancel { \text { g h } _2 \text o } } =2.05 \times 10^ { -2 } \ , \text { mol h } _2 \text o $ step $ 3 $ . convert moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ we can convert the moles of water to moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ using the mole ratio from the balanced reaction . $ \text { mol of bacl } _2 \cdot 2 \text h_2 \text o=2.05 \times 10^ { -2 } \ , \cancel { \text { mol h } _2 \text o } \times \dfrac { 1\ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o } { 2 \ , \cancel { \text { mol h } _2 \text o } } =1.03 \times 10^ { -2 } \ , \text { mol bacl } _2 \cdot 2 \text h_2 \text o $ step $ 4 $ . convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams since we want to find the mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ , we will need to know the mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample . we can convert moles of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ to mass in grams using the molecular weight of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . $ \text { mass of bacl } _2 \cdot 2 \text h_2 \text o=1.03 \times 10^ { -2 } \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } \times \dfrac { 244.47\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o } { 1 \ , \cancel { \text { mol bacl } _2 \cdot 2 \text h_2 \text o } } =2.51\ , \text { g bacl } _2 \cdot 2 \text h_2 \text o $ step $ 5 $ . calculate mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ in the original sample the mass percent can be calculated using the ratio of the mass from step $ 4 $ and the original sample mass . $ \text { mass % bacl } _2 \cdot 2 \text h_2 \text o=\dfrac { 2.51\ , \cancel { \text g } \text { bacl } _2 \cdot 2 \text h_2 \text o } { 9.51\ , \cancel { \text g } \text { of mixture } } \times 100\ % =26.4\ % \ , \text { bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~\text { ( no thanks to igor ! ) } $ shortcut : we could also combine steps $ 2 $ to $ 4 $ into a single calculation ( with the caveat that we should pay extra close attention to our units ) . in order to convert the mass of $ \text h_2 \text { o } $ to mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ ( which i will call `` hydrate '' in the calculation to save some space ) , we could solve the following expression : $ \text { mass of hydrate } ~=~\underbrace { 0.37\ , \cancel { \text { g h } _2 \text o } ~\times~ \dfrac { 1 \ , \cancel { \text { mol h } _2 \text o } } { 18.02\ , \cancel { \text { g h } _2 \text o } } } ~\times~\underbrace { \dfrac { 1\ , \cancel { \text { mol hydrate } } } { 2 \ , \cancel { \text { mol h } _2 \text o } } } ~\times~\underbrace { \dfrac { 244.47\ , \text { g hydrate } } { 1 \ , \cancel { \text { mol hydrate } } } } ~=~2.51\ , \text { g hydrate } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 2 : } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { step 3 : } ~~~~~~~~~~~~~~~~~~~~~~\text { step 4 : } $ $ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { find mol h } _2\text { o } ~~~~~~~~~~~~~~~~~~~~\text { use mole ratio } ~~~~~~~\text { find g bacl } _2 \cdot 2 \text h_2 \text o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ $ potential sources of error we just successfully used gravimetric analysis to calculate the purity of a mixture , hooray ! however , sometimes when you are in lab , things might not go quite so smoothly . things that could go wrong include : stoichiometry errors , such as not balancing the equation for the dehydration of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ lab errors , such as not giving the water enough time to evaporate or forgetting to tare a piece of glassware what would happen to our answer for the above situations ? situation $ 1 $ : we forgot to balance the equation in this situation , we would end up using the wrong mole ratio in the calculation in step $ 3 $ . instead of using the correct ratio of $ \dfrac { 2 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ , we would use the ratio $ \dfrac { 1 \ , \text h_2 \text o } { 1 \ , \text { bacl } _2 \cdot 2 \text h_2 \text o } $ . that would double the moles of metal hydrate calculated in step $ 3 $ , which will also double our overall mass percent of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ . ultimately , we would end up concluding that our sample has a much higher purity than it actually does ! concept check : what mass of metal hydrate would we calculate in situation $ 1 $ ? the moral of this story ? double check that all equations are properly balanced ! situation $ 2 $ : we ran out of time and not all the water evaporated in the second situation , we did not fully dehydrate our sample . this could happen for a lot of reasons , unfortunately . for example , we could run out of time , the heat could be set too low , or maybe we just took the sample off the heat before it was done by mistake . how does that affect our calculations ? in this situation , the difference in mass we calculate in step $ 1 $ will be lower than it should be , so we will have correspondingly fewer moles of water in step $ 2 $ . that will result in calculating a lower percent mass of $ \text { bacl } _2 \cdot 2 \text h_2 \text o $ compared to fully dehydrating the sample . in the end , we will end up underestimating the purity of the metal hydrate . chemists usually try to avoid situation $ 2 $ by drying to constant mass . that means monitoring the change in mass during the drying period until you no longer observe any further change in mass ( which also depends on the accuracy of your lab balance ) . when you first start heating your sample , you might expect to see a significant mass decrease as water is lost . as you continue to heat the sample , the change in mass gets smaller since there is less water left in the sample to evaporate . at some point , there won ’ t be enough water left to make a significant change in mass , so the measured mass will stay approximately constant over multiple measurements . at that point , you can hopefully assume your sample is dry ! lab tip : surface area is always a factor when removing volatiles from a sample . having a higher surface area will increase the rate of evaporation . you can increase the surface area of the sample by spreading your sample as thinly as possible on the heating surface or breaking up any larger chunks of solid , since moisture can get trapped inside the chunks . summary gravimetric analysis is a class of lab techniques that uses changes in mass to calculate the amount or concentration of an analyte . one type of gravimetric analysis is called volatilization gravimetry , which measures the change in mass after removing volatile compounds . an example of volatilization gravimetry would be using the change in mass after heating to calculate the amount or purity of a metal hydrate . some useful tips for gravimetric analysis experiments and calculations are : double check stoichiometry and make sure equations are balanced . when removing volatiles from a sample , make sure to dry to constant mass . always tare your glassware ! to read more about another common type of gravimetric analysis , see this article on precipitation gravimetry .
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what is gravimetric analysis ? gravimetric analysis is a class of lab techniques used to determine the mass or concentration of a substance by measuring a change in mass .
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how to minimize impurities in gravemetric analysis ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers !
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in example 4 , z^6 = -27 , it says that it is suppose to rotate 180 degrees because of the negative sign ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ?
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in the example 2 , can those points make a spiral ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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how do i determine what to add to ( 360 ) k ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all .
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can someone explain why if we are cubing cos ( 60 ) we get 180 degrees ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers !
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when solving z^6= -27 , how do i know the angle is 180 degrees ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle .
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in general , how do i find the angle when i have to solve z^n=w ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ .
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is a summary review in order here ?
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connection between $ i^2 = -1 $ and where $ i $ lives we began our study of complex numbers by inventing a number $ i $ that satisfies $ i^2 = -1 $ , and later visualized it by placing it outside the number line , one unit above $ 0 $ . with the visualizations offered in the last article , we can now see why that point in space is such a natural home for a number whose square is $ -1 $ . you see , multiplication by $ i $ gives a $ 90^\circ $ rotation about the origin : you can think about this either because $ i $ has absolute value $ 1 $ and angle $ 90^\circ $ , or because this rotation is the only way to move the grid around ( fixing $ 0 $ ) which places $ 1 $ on the spot where $ i $ started off . so what happens if we multiply everything in the plane by $ i $ twice ? it is the same as a $ 180^\circ $ rotation about the origin , which is multiplication by $ -1 $ . this of course makes sense , because multiplying by $ i $ twice is the same as multiplying by $ i^2 $ , which should be $ -1 $ . it is interesting to think about how if we had tried to place $ i $ somewhere else while still maintaining its characteristic quality that $ i^2 = -1 $ , we could not have had such a clean visualization for complex multiplication . powers of complex numbers let 's play around some more with repeatedly multiplying by some complex number . example 1 : $ ( 1 + i\sqrt { 3 } ) ^3 $ take the number $ z = 1 + i\sqrt { 3 } $ , which has absolute value $ \sqrt { 1^2 + ( \sqrt { 3 } ) ^2 } = 2 $ , and angle $ 60^\circ $ . what happens if we multiply everything on the plane by $ z $ three times in a row ? everything is stretched by a factor of $ 2 $ three times , and so is ultimately stretched by a factor of $ 2^3 = 8 $ . likewise everything is rotated by $ 60^\circ $ three times in a row , so is ultimately rotated by $ 180^\circ $ . hence , at the end it 's the same as multiplying by $ -8 $ , so $ ( 1 + i\sqrt { 3 } ) ^3 = -8 $ . we can also see this using algebra as follows : $ \begin { align } & amp ; \phantom { = } \left ( 2 ( \cos ( 60^\circ ) + i\sin ( 60^\circ ) ) \right ) ^3\\ & amp ; = 2^3 ( \cos ( 60^\circ + 60^\circ + 60^\circ ) + i\sin ( 60^\circ + 60^\circ + 60^\circ ) \\\ & amp ; = 8 ( \cos ( 180^\circ ) + i\sin ( 180^\circ ) ) \\ & amp ; = -8 \end { align } $ example 2 : $ ( 1 + i ) ^8 $ next , suppose we multiply everything on the plane by $ ( 1 + i ) $ eight successive times : since the magnitude of $ 1 + i $ is $ |1 + i| = \sqrt { 1^2 + 1^2 } = \sqrt { 2 } $ , everything is stretched by a factor of $ \sqrt { 2 } $ eight times , and hence is ultimately stretched by a factor of $ ( \sqrt { 2 } ) ^8 = 2^4 = 16 $ . since the angle of $ ( 1 + i ) $ is $ 45^\circ $ , everything is ultimately rotated by $ 8 \cdot 45^\circ = 360^\circ $ , so in total it 's as if we did n't rotate at all . therefore $ ( 1 + i ) ^8 = 16 $ . alternatively , the way to see this with algebra is $ \begin { align } & amp ; \phantom { = } ( 1 + i ) ^8 \\ & amp ; = \left ( \sqrt { 2 } \cdot ( \cos ( 45^\circ ) + i \sin ( 45^\circ ) \right ) ^8 \ & amp ; = ( \sqrt { 2 } ) ^8 \cdot \left ( \cos ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) + i\sin ( \underbrace { 45^\circ + \cdots + 45^\circ } { \text { $ 8 $ times } } ) \right ) \\ & amp ; = 16 \left ( \cos ( 360^\circ ) + i\sin ( 360^\circ ) \right ) \\ & amp ; = 16 \end { align } $ example 3 : $ z^5 = 1 $ now let 's start asking the reverse question : is there a number $ z $ such that after multiplying everything in the plane by $ z $ five successive times , things are back to where they started ? in other words , can we solve the equation $ z^5 = 1 $ ? one simple answer is $ z = 1 $ , but let 's see if we can find any others . first off , the magnitude of such a number would have to be $ 1 $ , since if it were more than $ 1 $ , the plane would keep stretching , and if it were less than $ 1 $ , it would keep shrinking . rotation is a different animal , though , since you can get back to where you started after repeating certain rotations . in particular , if you rotate $ \dfrac { 1 } { 5 } $ of the way around , like this then doing this $ 5 $ successive times will bring you back to where you started . the number which rotates the plane in this way is $ \cos ( 72^\circ ) + i\sin ( 72^\circ ) $ , since $ \dfrac { 360^\circ } { 5 } = 72^\circ $ . there are also other solutions , such as rotating $ \dfrac { 2 } { 5 } $ of the way around : or $ \dfrac { 1 } { 5 } $ of the way around the other way : in fact , beautifully , the numbers which solve the equation form a perfect pentagon on the unit circle : example 4 : $ z^6 = -27 $ looking at the equation $ z^6 = -27 $ , it is asking us to find a complex number $ z $ such that multiplying by this number $ 6 $ successive times will stretch by a factor of $ 27 $ , and rotate by $ 180^\circ $ , since the negative indicates $ 180^\circ $ rotation . something which will stretch by a factor of $ 27 $ after $ 6 $ applications must have magnitude $ \sqrt [ 6 ] { 27 } = \sqrt { 3 } $ , and one way to rotate which gives $ 180^\circ $ after $ 6 $ applications is to rotate by $ \dfrac { 180^\circ } { 6 } = 30^\circ $ . therefore one number that solves this equation $ z^6 = -27 $ is $ \begin { align } \sqrt { 3 } ( \cos ( 30^\circ ) + i\sin ( 30^\circ ) ) & amp ; = \sqrt { 3 } \left ( \frac { \sqrt { 3 } } { 2 } + i \frac { 1 } { 2 } \right ) \ & amp ; = \frac { 3 } { 2 } + i \frac { \sqrt { 3 } } { 2 } \end { align } $ however , there are also other answers ! in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle . the reason this matters is because it can affect the value of $ \dfrac { \theta } { n } $ if we replace $ \theta $ with $ \theta + 2\pi k $ before dividing . hence all the answers will be of the form $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta + 2k\pi } { n } \right ) + i\sin\left ( \dfrac { \theta + 2k\pi } { n } \right ) \right ) $ for some integer value of $ k $ . these values will be different as $ k $ ranges from $ 0 $ to $ n-1 $ , but once $ k=n $ we can note that the angle $ \dfrac { \theta + 2n\pi } { n } = \dfrac { \theta } { n } + 2\pi $ is really the same as $ \dfrac { \theta } { n } $ , since they differ by one full rotation . therefore one sees all the answers just by considering values of $ k $ ranging from $ 0 $ to $ n-1 $ .
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in fact , those answers form a perfect hexagon on the circle with radius $ \sqrt { 3 } $ : can you see why ? solving $ z^n= w $ in general let 's generalize the last two examples . if you are given values $ w $ and $ n $ , and asked to solve for $ z $ , as in the last example where $ n=6 $ and $ w = -27 $ , you first find the polar representation of $ w $ : $ w = r ( \cos ( \theta ) + i\sin ( \theta ) ) $ this means the angle of $ z $ must be $ \dfrac { \theta } { n } $ , and it 's magnitude must be $ \sqrt [ n ] { r } $ , since this way multiplying by $ z $ a total of $ n $ succesive times will in effect rotate by $ \theta $ and scale by $ r $ , just as $ w $ does , so $ z = \sqrt [ n ] { r } \cdot \left ( \cos\left ( \dfrac { \theta } { n } \right ) + i\sin\left ( \dfrac { \theta } { n } \right ) \right ) $ to find the other solutions , we keep in mind that the angle $ \theta $ could have been thought of as $ \theta + 2\pi $ , or $ \theta + 4\pi $ , or $ \theta + 2k\pi $ for any integer $ k $ , since these are all really the same angle .
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in the section `` solving z^n= w in general '' , why is the range 0 to n-1 ?
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