For the equilibrium system below, which of the following would result in an increase in the concentration of CO(g)?

Question

2H2(g) + CO(g) CH3OH(g) + 92 kJ
a) decreasing temperature
b) adding some CH3OH
c) both b and d
d) decreasing the volume of the container
e) both a and b

Answer 1

In "real" day to day talk (not chemical talk), Le Chatelier's Principle says that is we do something to a system at equilibrium, the system tries to undo what we've done. SO, as an example, adding H2 and the system will try to undo that. How can it do that. It can use up H2. How can it do that? By making more H2 and CO react to form more CH3OH. What about adding heat. The system will try to undo that; how can it do that? It will try to use the extra heat that we've added and it can do that by making the reaction shift to the left. As a result, CH3OH will be decreased, T will be decreased, H2 and CO will be increased. Using these two examples you should be able to answer the question. One point not emphasized above is about volume changes. If we decrease the volume of the container we must have increased the pressure (remember Boyle's Law). So the system will try to undo that by decreasing the pressure. It does that by shifting to the side with the smaller number of moles. In the above example that means a shift to the right (3 moles on the left and two on the right)