Consider this system at equilibrium.

A (aq) B (aq) deltaH=-750kJ/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 D) Q E) Q=K because neither charged

How will the system respond to a temperature increase?

A) shift left

B) shift right

C) no change

a) Q>K because K decreased

b) shift left

Explanation:

According to Van't Hoff equation

d (ln K) / dT = ΔH/RT²

since ΔH< 0 (exothermic reaction), then d (ln K) / dT < 0 → K decreases with an increase in temperature

thus

a) Since Q represents the product of concentrations, and assuming an increase in temperature do not affect significantly the concentration of products in a liquid state, then Q remains approximately constant, but K decreases → Q>K because K decreased

(thus ΔG is positive and ΔG is negative for the reverse reaction → products will produce reactants until the new equilibrium is reached)

b) Since K decreased, the system will shift towards the reactants and thus it will shift to the left