# What does a change in temperature do to the concentration of gases at equilibrium?

I am confused about a specific part of Le Chatelier's Principle. My question revolves around a homework assignment question:

$$\ce{2SO2(g) + O2(g) <=> 2SO3(g)} \qquad\Delta H^\circ = -198.2\:\mathrm{\frac{kJ}{mol}}$$

Comment on the changes in the concentrations of $\ce{SO2}$, $\ce{O2}$, and $\ce{SO3}$ at equilibrium if we were to increase the temperature of the system.

Now I understand that increasing the temperature of an exothermic process will cause the equilibrium to shift towards the left (in the direction of the endothermic reaction); however, what does the temperature do to the concentrations of the gases? I think it does nothing, but I am not sure.

You are correct in saying that the increase in temperature causes the equilibrium to shift to the left, in the direction of the endothermic reaction. As the reaction continues in the endothermic direction, the concentrations of $\ce{SO3}$ will decrease in favour of the evolution of more $\ce{SO2}$ and $\ce{O2}$, due to the additional heat available.