OG CP #3

[663697]

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I got this one correct but I was stuck between D and B during the test. I thought that according to:

, Keq should increase as T increases. Why is this not the case? I've been confused about G and G(0) recently so I suspect this is the cause of my confusion with this question.

 

[Nugester]

I think it is easy to keep it simple. So you have:

1 + 2 <=> 3 + 4

Adding more 3 would shift the reaction back to the left, while adding 2 would shift it back to the right unless I'm missing something.

As for increasing or decreasing temperature and its affects on Keq depend on:

1 + 2 + heat<=> 3 + 4 or 1 + 2 <=> 3 +4 + heat (whether it is an endothermic/exothermic reaction)

 

[aldol16]

You have no idea what the delta G(0) of this reaction is. If it were given that the delta G(0) is positive, then increasing T would indeed increase Keq. But if delta G(0) is negative, then increasing T would decrease Keq.

 

[rabbott1971]

It is a pure Le Chatelier problem. The correct answer is the only one that would increase the specified product, by adding reactants that create it. In my gen chem II class, the guy said you can think of heat as a chemical species in these situations. So if you have to add heat (endothermic), then heat is a reactant. If heat is released (exothermic), then heat is a product. Then you can just apply the Le Chatelier considerations to heat. In your problem, heat is not mentioned, so you can't know, and therefore it can't be the correct answer.