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3 aName the method of gas collection used |
Over water |
Upward delivery |
Down ward displacement of water |
bWhat property of Oxygen makes it to be collected using the method above |
Slightly soluble in water |
4 What is the purpose of manganese IV oxide |
Manganese IV oxide is catalyst |
A catalyst is a substance that speeds up the rate of a chemical reaction but remain chemically unchanged at the end of the reaction |
Hydrogen peroxide decomposes slowly to form water and Oxygen gas |
A little Manganese IV oxide speeds up the rate of decomposition by reducing the time taken for a given volume of Oxygen to be produced |
5 Write the equation for the reaction |
Hydrogen peroxide Water Oxygen |
2H2O2 aq 2H2O l O2 g |
6 Lower a glowing splint slowly into a gas jar containing Oxygen gas State what is observed |
The glowing splint relightsrekindles |
Oxygen relightsrekindles a glowing splint This is the confirmatory test for the presence of Oxygen gas |
Method 1 Using Sodium peroxide |
Half fill a troughbasin with tap water Add four drops of phenolphthalein indicator |
Place a bee hive shelfstand into the water |
Completely fill a gas jar with water and invert in onto the bee hive shelfstand |
Clamp a round bottomed flask and set up the apparatus as below |
Collect several gas jars of Oxygen covering each sample |
Sample observation questions |
1 What is observed when water is added |
i Into the flask containing sodium peroxide |
Rapid effervescencebubblingfizzing |
ii Phenolphththalein |
Remains colourless Phenolphthalein indicator is colourless in neutral solution |
2 Describe the colour and smell of the gas |
Colourless and odorless |
3aName the method of gas collection used |
Over water Oxygen is slightly soluble in water |
4 Test the gas by lowering a glowing splint slowly into a gas jar containing the prepared sample |
The glowing splint relightsrekindles This confirms the presence of Oxygen gas |
5 Write the equation for the reaction |
Sodium peroxide Water Sodium hydroxide Oxygen |
2Na2O2 aq 2H2O l 4NaOH aq O2 g |
1 Test the gas by lowering a glowing splint slowly into a gas jar containing the prepared sample |
The glowing splint relightsrekindles |
This confirms the presence of Oxygen gas |
2 Write the equation for the reaction |
Potassium Chlorate V Potassium Chloride Oxygen |
2KClO3 aq 2KCl aq 3O2 g |
3 What is the purpose of manganese IV oxide |
Manganese IV oxide is catalyst |
A catalyst is a substance that speeds up the rate of a chemical reaction but remain chemically unchanged at the end of the reaction |
Potassium Chlorate V decomposes slowly to form potassium chloride and Oxygen gas |
A little Manganese IV oxide speeds up the rate of decomposition by reducing the time taken for a given volume of Oxygen to be produced |
cUses of Oxygen |
1 Oxygen is put in cylinders for use where natural supply is not sufficiently enough This is mainly in |
iMountain climbingMountaineeringat high altitudes the concentration of airoxygen is low Mountain climbers must therefore carry their own supply of oxygen for breathing |
ii Deep sea divingDeep sea divers carry their own supply of Oxygen |
iii Saving life in hospitals for patients with breathing problems and during anesthesia |
2 A mixture of oxygen and some other gases produces a flame that is very hot |
i Oxyacetyleneethyne flame is produced when Ethyneacetylene gas is burnt in pure oxygen The flame has a temperature of about 3000oCIt is used for welding cutting metals |
iiOxyhydrogen flame is produced when Hydrogen is burn in pure oxygen The flame has a temperature of about 2000oCIt is used also for welding cutting metals |
3 Oxyhydrogen mixture is used as rocket fuel |
4 A mixture of charcoal petrol and liquid Oxygen is an explosive |
d Chemical properties of Oxygen combustion |
Oxygen is a very reactive non metal Many elements react with oxygen through burning to form a group of compounds called Oxides |
Burningcombustion is the reaction of Oxygen with an elementsubstances |
Reaction in which a substance is added oxygen is called Oxidation reaction Burningcombustion are an example of an oxidation reaction |
Most non metals burn in Oxygenair to form an Oxide which in solution dissolved in water is acidic in nature They turn blue litmus redeg Carbon IV oxideCO2 Nitrogen IV oxide NO2 Sulphur IV oxide SO2 |
Some non metals burn in Oxygenair to form an Oxide which in solution dissolved in water is neutral in nature They dont turn blue or red litmus Eg Carbon II oxideCO Water H2O |
All metals burns in Oxygenair to form an Oxide which in solutiondissolved in water is basicalkaline in nature They turn red litmus blueeg |
Magnesium oxideMgO Sodium Oxide Na2O Copper II oxideCuO Elementssubstances burn faster in pure Oxygen than in air |
Air contains the inactive part of air that slows the rate of burning of substanceselements |
iReaction of metals with Oxygenair |
The following experiments show the reaction of metals with Oxygen and air |
I Burning Magnesium |
Procedure |
aCut a 2cm length piece of magnesium ribbon Using a pair of tongs introduce it to a Bunsen flame Remove it when it catches fire Observe |
Place the products in a beaker containing about 5cm3 of water Test the solutionmixture using litmus papers |
bCut another 2cm length piece of magnesium ribbon Using a pair of tongs introduce it to a Bunsen flame When it catches fire lower it slowly into a gas jar containing Oxygen |
Place about 5cm3 of water into the gas jar Test the solutionmixture using litmus papers Test the solutionmixture using litmus papers |
Observations |
aIn air |
Magnesium burns with a bright blindening flame in air forming white solidash powder Effervescencebubbles fizzing Pungent smell of urine Blue litmus paper remains blue Red litmus paper turns blue |
b In pure Oxygen |
Magnesium burns faster with a very bright blindening flame pure oxygen forming white solidash powder No effervescencebubbles fizzing No pungent smell of urine Blue litmus paper remains blue Red litmus paper turns blue |
Explanation |
Magnesium burns in air producing enough heat energy to react with both Oxygen and Nitrogen to form Magnesium Oxide and Magnesium nitride Both Magnesium Oxide and Magnesium nitride are white solidash powder |
Chemical equations |
Magnesium Oxygen Magnesium Oxide |
2Mgs O2g 2MgOs |
Magnesium Nitrogen Magnesium Nitride |
3Mgs N2g Mg3N2 s |
Magnesium Oxide dissolves in water to form a basicalkaline solution of Magnesium hydroxide |
Chemical equations |
Magnesium Oxide Water Magnesium hydroxide |
2Mgs O2 l 2MgOs |
Magnesium Nitride dissolves in water to form a basicalkaline solution of Magnesium hydroxide and producing Ammonia gas Ammonia is also an alkalinebasic gas that has a pungent smell of urine |
Chemical equations |
Magnesium Nitride Water Magnesium hydroxide Ammonia gas |
Mg3N2 s 6H2O l 3Mg OH2 aq 2NH3g |
II Burning Sodium |
Procedure |
aCarefully cut a very small piece of sodium Using a deflagrating spoon introduce it to a Bunsen flame Remove it when it catches fire Observe |
Place the products in a beaker containing about 20cm3 of water Test the solutionmixture using litmus papers |
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