Homework Help: Chemistry

Posted by Tracy on Monday, March 5, 2012 at 10:28pm.

Consider this system at equilibrium.
A(aq) <-> B(aq) Delta H = +750 kJ/mol ..
What can be said about Q and K immediately after an increase in temperature?
a] Q > K because Q increased..
b] Q>K because K decreased..
c] Q<K because Q decreased..
d] Q<K because K increased..
e] Q=K because neither changed

How will the system respond to the temperature increase?
a] shift to the left
b] shift to the right
c] no change

I said that it would shift to the left for the second part [i think] but for the first part i'm not sure because my notes says that adding temperature would cause the reactant concentrations to increase; thus, equilibrium constant K will decrease.

doesn't that mean that a AND b are both correct..? but there can only be one answer from part 1.. please help me reason!

Chemistry - Tracy, Monday, March 5, 2012 at 10:32pm
and for the sake of understanding.. can someone tell me what would happen if the reaction was exothermic instead of endothermic?
Chemistry - DrBob222, Monday, March 5, 2012 at 11:46pm
A + heat ==> B
K or Q = (B)/(A)

I may not have interpreted this correctly because I'm not positive a delta T could make an IMMEDIATE impact; however, if we look at the long term, it MUST shift to the right because it's an endothermic reaction and heat is being added. So in the long term B will go up, A will go down, which means K will get larger. Therefore, in the short term Q is too small so Q < what K will be.
The reasoning is the reverse for an exothermic. reaction.
Chemistry - Tracy, Tuesday, March 6, 2012 at 5:37am
thank you Dr. Bob!

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