Homework problem 7

[805377003]

Consider this system at equilibrium.

A(aq)↽−−⇀B(aq)ΔH=+550 kJ/mol

What can be said about Q and K immediately after an increase in temperature?

Q > K because K decreased.

Q < K because K increased.

Q > K because Q increased.

Q < K because Q decreased.

Q = K because neither changed.
How will the system respond to a temperature increase?

shift left

shift right

no change

[Kayla Law 2D]

A change in temperature causes K to change. Since this reaction requires heat, it is endothermic. Because the forward reaction is endothermic, heating the system will favor the forward reaction and product formation (additional heat is used). Due to this, K will be a larger value since the formation of product is favored more than it was before (at equilibrium, the ratio of [product]/[reactant] will be greater than it was before since the formation of product is more favored). Therefore, Q < K because K increased. The system will shift to the right and favor the forward reaction. Hope this helps! :)

[Anirudh Mahadev 1G]

I agree with the above answer, but also if a reaction is endothermic you can think of heat as a reactant, so increasing temperature a.k.a adding heat, will act like adding a reactant. The denominator will be larger and Q will be less than K, and the reactant shifts towards the products.

[Morgan Gee 3B]

Heat (energy) is required for the forward reaction to occur and an increase in the temperature is equivalent to an increase in energy. As a result, the forward reaction will occur at a greater rate. This can be used to help indicate that Q < K as we know that in that scenario the reaction "shifts to the right".

[Anh Trinh 1J]

Adding on to this, raising the temperature of an exothermic reaction lowers the value of K, while raising the temperature of an endothermic reaction increases the value of K. So for exothermic (heat releasing) reactions, when the temperature is raised the composition of the equilibrium mixture shifts in favor of reactants, so K decreases. And for endothermic (heat absorbing) reactions, K increases.