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Gibbs energy: the term −TdS. Where does the reversible heat go? |
To aquire the yellow colour of vanadium ion, it must be present in a 5+ oxdiation state.
This can be acheived (according to my textbook) by adding dilute sulfuric acid to $\ce{NH4VO3}$, then followed by zinc.
$$\ce{VO3- (aq) + 2H+ (aq) -> VO2^{+} (aq) + H2O (l)}$$
where $\ce{VO2^{+}}$ gives the yellow colour f... |
From my class text book:
>The oxidation states of Vanadium ions 5+ and 4+ are shown in the compounds $\ce{VO2^{+}}$ and $\ce{VO^{2+}}$ respectively, whereas $\ce{V^{3+}}$ and $\ce{V^{2+}}$ are shown like this in the redox reaction (reduction half equation).
Why is this? cannot $\ce{V^{5+}}$ and $\ce{V^{4+}}$ exi... |
I read this in an old chemistry book. It says:
>When selenium is dropped into melted phosphorus, it dissolves rapidly, and the compound sinks through the liquid phosphorus in red streaks.
My question is whether the phosphorus is red or white? |
I was reviewing many electron computational methods recently and got a bit confused about relation between different approaches. In particular in what is essential elemental difference between Hartree-Fock (HF) and tight binding (TB) for example? It could be stupid question, sorry, I am not that deeply familiar with th... |
The following question was given in FIITJEE study material:
> [![enter image description here][1]][1]
I guess **(i)** step is de-esterification, which gives the compound of option **(A)**.
In next step, I wouldn't expect it to decarboxylate, instead I guess it'll dehydrate. So, according to me, final product i... |
I viewed an image showing all the possible oxidation states of each element in the first row of transition metals, and the main oxidation states highlighted in a different colour.
I noticed all elements Sc to Cr had in common a 3+ main oxidation state,
and from Mn to Zn 2+ was the common main oxidation state.
... |
Why does 2+ oxidation state become more stable relative to 3+ oxidation state for first row of transition metals? |
I know nothing about chemistry, I managed not to take it in correspondence high school. I don’t know how to read or make sense of this: $\ce{CuAl6(PO4)4(OH)8.4H2O}$ the chemical formula of turquoise. From looking at a children’s periodic table I figured out some of the letters like Copper and aluminum, but I don’t know... |
I know that salt makes ice melt, but why does salt make the ice not refreeze?
I have tried all different kinds of experiments, but I still cannot figure it out. |
I know that salt makes ice melt, but why does salt make the ice not refreeze?
I have tried all different kinds of experiments, but I still cannot figure it out.
The chloride acid in the salt makes the ice melt. Which then makes the ice colder than it was before we put the salt on the ice. |
I know that salt makes ice melt, but why does salt make the ice not refreeze?
I have tried all different kinds of experiments, but I still cannot figure it out.
The chloride acid in the salt makes the ice melt. What makes then the ice colder than it was before we put the salt on the ice? |
What in salt makes ice unable to refreee? |
I have been recently reading a lot on the quantum mechanical theory regarding DFT and TDDFT (Oscillatory and Rotatory Strengths in particular) in order to understand how first principle calculations fundamental theory work.
I get that DFT is used to calculate the ground-state configuration of a system and TDDFT ... |
Can you explain DFT and TDDFT functioning (math aside)? |
I have been recently reading a lot on the quantum mechanical theory regarding Density Functional Theory, DFT, and Time Dependent Density Functional Theory, TDDFT (Oscillatory and Rotatory Strengths in particular) in order to understand how first principle calculations fundamental theory work.
I get that DFT is use... |
What in salt makes ice unable to refreeze? |
what is "salpotricon"? |
The question of how vinegar + hydrogen peroxide + table salt can be used to etch copper has been asked before (https://chemistry.stackexchange.com/questions/102156/full-equation-when-using-vinegar-hydrogen-peroxide-and-salt-to-etch-copper). However, the accepted answer seems to miss a key fact when observing this react... |
What gas is evolved when using vinegar, hydrogen peroxide, and salt to etch copper, and why? |
[![enter image description here][1]][1]
[1]: https://i.stack.imgur.com/zoUp7.jpg
My textbook simply says:
>Since an ionic compound consists of equal number of positive and negative ions, the overall charge of an ionic compound is zero.
But why is the number of positive and negative ions equal?
Can’t ... |
I recently learnt that electronegativity generally decreases as I move down a group and from right to left within a period. However, according to the table below, Pb has an electronegativity of $2.33$, which is higher than $1.96$ of Sn. There are also a lot other elements, such as Au, Hg, and W, that does not follow th... |
Why does Pb have a higher electronegativity than Sn? |
[![Molecule][1]][1]
[1]: https://i.stack.imgur.com/28RBf.png
I'm trying to figure out whether this is in R/S configuration....I thought it would be R since the groups seem to be decreasing in priority in the clockwise direction (since F has the largest atomic number). However, the answers say that it is actua... |
What is the priority order of the four groups? |
PubChem is unable to generate the conformers of [*Z*-6-Heneicosen-11-one][1]? The website says that the molecule is **too flexible**
**What does flexibility of a molecule mean in this context**? I understand that it is a long chain compound, but I assumed that the bonds are rigid and do not flex? In layman’s terms, ... |
For a given crystal structure, say body centred cubic, on what factors does surface energy of each plane depend?
A basic approach considers the atomic density on each crystallographic plane, the number of bonds broken if the surface is cleaved along that plane and combines these two.
Is this a realistic and reasona... |
I'm trying to explain how a change in temperature favours an endothermic/exothermic reaction from a collision theory point of view, but I'm not really familiar with the concept just yet. For an increase in temperature, can I say that:
> An increase in temperature leads to a greater frequency of collisions between re... |
How to explain that an increase in temperature favours an endothermic reaction? |
My experiments results showed that the voltage decreases down Group 1 chlorine salts in the salt bridge. All other variables were kept constant. Zinc and Copper rods were used. Concentrations of the salt in the salt bridge were 1M.
I dont understand this result. What could the reason be behind this? |
Why does changing the salt of the salt bridge (group 1 chlorine salts) effect the voltage produced in a galvanic cell? |
For a given crystal structure, say body centred cubic, on what factors does surface energy of each plane depend?
A basic approach considers the atomic density on each crystallographic plane, the number of bonds broken if the surface is cleaved along that plane and combines these two.
Is this a realistic and reasona... |
The coordination number refers to the number of binders that interact with the central metal ion. So, in the complex $\ce{[Cr(C_{2}O_{4})_3]^{3-}}$ chromium is bound to three oxalate ions.
Why its coordination number is considered 6? So, is it an incorrect definition of coordination number?
Can you help me?
Tha... |
To be clear I am not talking about zero-point energy.
I wish to understand how the energy of a system is calculated relative to a zero baseline. This is best explained with an example.
From DFT, the energy could be:
H2 = -6.5 eV,
Isolated H = -3 eV
What are these numbers related to? What would be a ... |
To be clear I am not talking about zero-point energy.
I wish to understand how the energy of a system is calculated relative to a zero baseline. This is best explained with an example.
From DFT, the energy could be:
H2 = -6.5 eV,
Isolated H = -3 eV
What are these numbers related to? What would be a ... |
Calcium crystals are semi-transparent but turn white when crushed. Why? I think that it has something to do with the scattering of all wavelengths of light from small particles. But that cannot be a complete story because any crushed substance (say, carbon) would have appeared white. |
Why do calcium crystals turn white upon crushing? |
Calcium crystals are semi-transparent but turn white when crushed. Why? I think that it has something to do with the scattering of all wavelengths of light from small particles. But that cannot be the whole story because then any crushed substance (say, carbon) would have appeared white. |
Calcite crystals are semi-transparent but turn white when crushed. I used to think that it has something to do with the scattering of all wavelengths of light from small particles. But that cannot be the whole story. By that explanation crushed carbon should also appear white (which is not the case).
So my question ... |
Why do some substances appear white when crushed while others do not? |
The coordination number refers to the number of binders that interact with the central metal ion. So, in the complex $\ce{[Cr(C2O4)3]^3-}$ chromium is bound to three oxalate ions.
Why its coordination number is considered 6? So, is it an incorrect definition of coordination number?
Can you help me? |
Some substances appear white when crushed while others do not. Why? |
I am trying to understand how the Gibbs energy change of a chemical reaction is computed and I do not understand why concentrations (mol/L) are used as a proxy for activity rather than mole fractions (mol/total mol).
From wikipedia (https://en.wikipedia.org/wiki/Chemical_potential), in an ideal solution, the chemica... |
how comes concentration is used as a proxy for activity instead of mole ratio? |
I am trying to understand how the Gibbs energy change of a chemical reaction is computed and I do not understand why concentrations (mol/L) are used as a proxy for activity rather than mole fractions (mol/total mol).
From the Wikipedia article on the [chemical potential](https://en.wikipedia.org/wiki/Chemical_potent... |
Why is concentration used as a proxy for activity instead of mole fraction? |
I am not talking about zero-point energy.
I wish to understand how the energy of a system is calculated relative to a zero baseline. This is best explained with an example.
From DFT, the energy could be:
H2 = -6.5 eV,
Isolated H = -3 eV
What are these numbers related to? What would be a system at ... |
What are computed energies in DFT and FF methods relative to? |
In vitro, long chain fatty acids may yield more energy when bonds break, but in vivo, I understood that energy is burned before unsaturated fatty acids can be oxidized because the side groups with double bonds are crowded, and bunched on one side in the cis position, as all unsaturated FA are, and the molecules of oxid... |
I am trying to understand how the Gibbs energy change of a chemical reaction is computed and I do not understand why concentrations (mol/L) are used as a proxy for activity rather than mole fractions (mol/total mol).
From the Wikipedia article on the [chemical potential](https://en.wikipedia.org/wiki/Chemical_potent... |
I am not talking about zero-point energy.
I wish to understand how the energy of a system is calculated relative to a zero baseline. This is best explained with an example.
From DFT, the energy could be:
H2 = -13.6 eV,
Isolated H = -31.8 eV
What are these numbers related to? What would be a system... |
What is "salpotricon"? |
It is intuitive to me that for a spontaneous process involving any system i.e. one occurring without constant human interaction $$ \text{d}S \geq 0 $$ as I can observe increasing energy dispersal in everyday life, for example my tea turning cold.
What is not intuitive to me is that for all systems $$ \text{d}S \geq ... |
As observed the reactivity of carbonyl derivatives with a nucleophile goes like
Acid halide>acid anhydride > acid>amide>ketone>aldehyde
So is nucleophile a code word to nucleophilic substitution
(Nucleophilic acyl substitution in this place)?
My professor gave the explanation by saying that look out of del+ charg... |
Helium is the only element which does not freeze at atmospheric pressure, and only forms a liquid at around 4 Kelvin due to weak van der Waals forces.
I'm interested in knowing roughly how much hybridization/bonding occurs in liquid helium (for example, hybridization energy in cm$^{-1}$ or electronvolts). I would gu... |
As observed, the reactivity of carbonyl derivatives with a nucleophile goes like
Acid halide > acid anhydride > acid > amide > ketone > aldehyde
So is nucleophile a code word to nucleophilic substitution
(Nucleophilic acyl substitution in this place)?
My professor gave the explanation by saying that look out of... |
As observed, the reactivity of carbonyl derivatives with a nucleophile goes like:
Acid halide > acid anhydride > acid > amide > ketone > aldehyde. So is nucleophile a code word to nucleophilic substitution (nucleophilic acyl substitution in this place)?
My professor gave the explanation by saying that look out of... |
I am asked this question:
>Write a balanced equation, including state symbols, for this reaction:
>$\ce{calcium + hydrochloric acid \implies calcium chloride hydrogen}$
I answered this:
> $\ce{Ca(s) + 2HCl(l) \implies 2CaCl(s) + H2}$
This was the answer:
> $\ce{Ca(s) + 2HCl(aq) + \implies CaCl2(aq) + ... |
How to determine the chemical state of a given chemical compound? |
I am asked this question:
>Write a balanced equation, including state symbols, for this reaction:
>$\ce{calcium + hydrochloric acid \implies calcium chloride hydrogen}$
I answered this:
> $\ce{Ca(s) + 2HCl(l) \implies 2CaCl(s) + H2}$
This was the correct answer:
> $\ce{Ca(s) + 2HCl(aq) + \implies CaCl... |
So if you put a mint mentos in a cup of soda it will explode everywhere. The mint in the mentos makes the soda have a chemical reaction which will then make the soda explode right? Well what would happen if we put a mento in different types of soda would that make a difference in how much chemical reation there will be... |
Why does a mentos make soda explode? |
I am asked this question:
>Write a balanced equation, including state symbols, for this reaction:
>$\ce{calcium + hydrochloric acid \implies calcium chloride hydrogen}$
I answered this:
> $\ce{Ca(s) + 2HCl(l) \implies 2CaCl(s) + H2}$
This was the correct answer:
> $\ce{Ca(s) + 2HCl(aq) + \implies CaCl... |
I am asked this question:
>Write a balanced equation, including state symbols, for this reaction:
>$\ce{calcium + hydrochloric acid \implies calcium chloride hydrogen}$
I answered this:
> $\ce{Ca(s) + 2HCl(aq) \implies CaCl2(s) + H2}$
This was the correct answer:
> $\ce{Ca(s) + 2HCl(aq) + \implies CaC... |
I read in a textbook (Mathematics for Physical Chemistry by D. McQuarrie) an example of Euler's Theorem used in Thermodynamics. The author states "The [variables] are all extensive [quantities], and so [Euler's theorem is applicable]" (I'll provide more details below)
<b>My question</b>: why do variables being <i>ex... |
I am asked this question:
>Write a balanced equation, including state symbols, for this reaction:
>$\ce{calcium + hydrochloric acid \implies calcium chloride hydrogen}$
I answered this:
> $\ce{Ca(s) + 2HCl(aq) \implies CaCl2(s) + H2}$
This was the correct answer:
> $\ce{Ca(s) + 2HCl(aq) + \implies CaC... |
How to determine the chemical state of a reactant or product in a chemical equation? |
The Gibbs energy has not been derived this way. It came from a thought process. About 100 years ago, Gibbs was puzzled by the very existence of spontaneous endothermic reactions. In mechanics, objects always fall down. They never "fall up" spontaneously. They never gets more energy spontaneously. In exothermic reaction... |
The Gibbs energy has not been derived this way. It came from a thought process. About 100 years ago, Gibbs was puzzled by the very existence of spontaneous endothermic reactions. In mechanics, objects always fall down. They never "fall up" spontaneously. They never gets more energy spontaneously. In exothermic reaction... |
The Gibbs energy has not been derived this way. It came from a thought process. About 100 years ago, Gibbs was puzzled by the very existence of spontaneous endothermic reactions. In mechanics, objects always fall down. They never "fall up" spontaneously. They never gets more energy spontaneously. In exothermic reaction... |
Actually, as some may recall that the action of Al with NaOH can lead to surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface chemistry and subsurface... |
**Overview:**
As of my knowledge from metallurgical thermodynamics a phase is a thermodynamically stable and homogeneous entity made up of different species of a given concentration.
e.g = 'Austenite' is a phase of steel with a given (Fe, C) concentration (%wt). So, we can call the Iron and carbon to be species. ... |
Difference between a species and a phase in a solution? |
Actually, as some may recall that the action of Al with NaOH can lead to surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface chemistry and subsurface... |
Actually, as some may recall that the action of Al with NaOH can lead to surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface chemistry and subsurface... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [2008 doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [2008 doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface... |
For a given crystal structure, say body centred cubic, on what factors does surface energy of each plane depend?
A basic approach considers the atomic density on each crystallographic plane, the number of bonds broken if the surface is cleaved along that plane and combines these two.
Is this a realistic and reasona... |
I've seen that the first ionization energy of a particular metal is always greater than its work function. This implies that the valence electrons in an isolated atom are more strongly bound than the de-localized conduction electrons in the solid metal.
>For example, the first ionization energy of sodium is $5.14\ma... |
It is now routine in the scientific community that "main-group hypervalent molecules, under certain conditions, tend to be better represented by resonance structures involving ionic bonds, rather than the utilisation of d-orbitals". For example, PF5 is better represented by a total of 5 "[PF4]+ [F]-" resonance structur... |
Why is estimation of sodium hydroxide more accurate with oxalic acid rather than with sulfuric acid or any other strong acid? |
In books it is commonly written that whenever a chemical bond is formed the energy of the molecules/atoms gets lowered and hence energy is released. This is generally explained by diagrams like this
[![enter image description here][1]][1]
But I'm really unable to understand this process, I accept that before b... |
Why energy is released when chemical bond is formed? |
How energy is released when chemical bond is formed? |
The following text is from Solomons, Fryhle and Snyder Organic Chemistry Third Edition, chapter 1 "The Basics: Bonding and Molecular Structure", page 13, topic 1.5 "Resonance Theory", sub topic 1.5B "Schematic Energy Level Diagrams of Some Mesomeric Molecules/Ions":
> Energy level diagrams of some resonating structu... |
What is the significance of the downward arrows in energy level diagrams in organic chemistry? |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [2008 doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [2008 doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [2008 doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. More precisely, let me quote from this [2008 doctoral thesis](http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=16827&context=rtd) " Alkaline dissolution of aluminum: surface... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. Related chemistry is commonly employed via the vigorous action of HCl on Zn (so one of the roles of zinc is to provide added surface area, to answer a posited question).
More ... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. Related chemistry is commonly employed via the vigorous action of HCl on Zn (so one of the roles of zinc is to provide added surface area, to answer a posited question).
More ... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. Related chemistry is commonly employed via the vigorous action of HCl on Zn (so one of the roles of zinc is to provide added surface area, to answer a posited question).
More ... |
Consider the following molecule:
[![MPH molecule][1]][1]
SMILES: `COC(=O)[C@@H](c1ccccc1)[C@@H]1CCCC[NH2+]1`
I would expect the computed partial chage on the amine to be positive, due to its protonation state.
When using Gasteiger charges calculator, it is affected a positive charge of 0.2422.
However,... |
I am trying to understand how the Gibbs energy change of a chemical reaction is computed and I do not understand why concentrations (mol/L) are used as a proxy for activity rather than mole fractions (mol/total mol).
From the Wikipedia article on the [chemical potential](https://en.wikipedia.org/wiki/Chemical_potent... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. Related chemistry is commonly employed via the vigorous action of HCl on Zn (so one of the roles of zinc is to provide added surface area, to answer a posited question).
More ... |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. Related chemistry is commonly employed via the vigorous action of HCl on Zn (so one of the roles of zinc is to provide added surface area, to answer a posited question).
More ... |
>Experimentally it was determined that extent of gas adsorption varies directly with pressure, and then it directly varies with pressure raised to the power 1/n until saturation pressure Ps is reached. Beyond that point, the rate of adsorption saturates even after applying higher pressure. Thus, the Freundlich adsorpti... |
Why Freundlich adsorption isotherms fails at high pressure conditions? |
More recent science (as compared to 1975), the action of Al with NaOH is believed to produce surface absorbed hydrogen atoms on the aluminum. Related chemistry is commonly employed via the vigorous action of HCl on Zn (so one of the roles of zinc is to provide added surface area, to answer a posited question).
More ... |
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