What happens to the following reaction at equilibrium if the pressure is decreased?

Question

2H2(g) + O2(g) 2H2O(g)

A. The equilibrium shifts left because Q < K.
B. The equilibrium shifts right because Q < K.
C. The equilibrium shifts right because Q > K.
D. The equilibrium shifts left because Q > K.

Answer 1

K = (H2O)^2/(H2)^2(O2)
In increase in P means the reaction will shift to the side with fewer mols. So increase in P shifts to the right; therefore, a decrease must shift to the left. There are two answers for left (A and D). Can you figures with Q is larger or smaller.