For the below reaction, which change(s) will increase the fraction of SO3(g) in the equilibrium mixture?

Question

Equation:

2SO2(g) + O2(g) yields 2SO3(g) change in H degrees is less than 0.

1. Increasing the pressure
2. Increasing the temperature
3. adding a catalyst

Answer 1

You can always apply LeChatlier's principle to problems like this. If you disturb and equilibrium, the reaction "shifts" to relieve the stress that you applied. This reaction is exothermic, and so you can think of "heat" as a product. So, increasing the temperature will shift the equilibrium to the left, DECREASING the SO3 amount. Catalysts cannot change an equilibrium. They can increase the rate of the reaction, but they increase the rate of both the forward and reverse reactions, so don't change the equilibrium concentrations. If you increase the pressure, you have 3 moles of gas on the left and only 2 on the right. Increasing pressure will shift the equilibrium toward the side with the fewest moles of gas, and so will increase the amount of SO3.

Answer 2

Increasing the pressure only.

Increasing the temperature will increase the fraction of SO2 and O2

Catalyst does not influence the equilibrium