The position of equilibrium
4 marks · NormalMethanol can be produced from carbon monoxide and hydrogen:
This reaction is reversible and carried out in a sealed container.
Explain what happens to the position of equilibrium when the temperature is increased, assuming the forward reaction is exothermic.
Describe how increasing the pressure will affect the position of equilibrium.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Equilibrium shifts to the left, favouring the endothermic reverse reaction; yield of methanol decreases.
(b) Equilibrium shifts to the side with fewer gas molecules (right), favouring the production of methanol; yield of methanol increases.
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Marking points
M1 (a) · 1 mark · Identifies equilibrium shifts left or towards the endothermic side when temperature increases.
A1 (a) · 1 mark · States the yield of methanol decreases.
M2 (b) · 1 mark · States equilibrium shifts to the side with fewer gas molecules (right/CH3OH).
A2 (b) · 1 mark · States the yield of methanol increases.
Worked solution
(a) If the temperature is increased, the equilibrium shifts to oppose the change (Le Chatelier's principle). The reverse reaction is endothermic, so equilibrium shifts to the left and the yield of methanol decreases.
(b) Increasing pressure shifts the equilibrium to the side with fewer gas molecules. The right-hand side (methanol) has fewer gas molecules (1 vs 3), so equilibrium shifts to the right and more methanol is formed.