Consider this system at equilibrium.

A (aq) B (aq)

Delta H = - 550 kL/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 a temperature increase?

1, shift left

2, shift right

3, no change

Q is the "reaction quotient" and is used to determine which way a given system will move to establish equilibrium. If the initial conditions give a Q which is larger than K, then the equilibrium will move to the left to establish equilibrium. If the value of Q is less than the value of K, then the system will move to the right to establish equilibrium. If Q happens to equal K, then the system is at equilibrium.

When equilibrium is re-established the value of K will be greater. Temperature changes are the only changes that actually change the value of K.