The position of equilibrium
4 marks · NormalAmmonia is made in the Haber process:
The forward reaction is exothermic.
Explain what happens to the yield of ammonia if the temperature is increased.
Describe and explain the effect of increasing pressure on the position of equilibrium.
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(a) Increasing temperature shifts equilibrium to the left (endothermic side), so the yield of ammonia decreases.
(b) Increasing pressure shifts equilibrium to the right (towards fewer gas molecules), favouring the production of ammonia (NH3).
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Marking points
M1 (a) · 1 mark · States equilibrium shifts to left/endothermic side when temperature increases.
A1 (a) · 1 mark · Links shift to a decrease in ammonia yield.
M2 (b) · 1 mark · States that increasing pressure shifts equilibrium to right/fewer molecules.
A2 (b) · 1 mark · Links shift to favouring production of ammonia.
Worked solution
(a) Increasing temperature favours the endothermic direction (left, decomposition of ammonia), so less ammonia is formed.
(b) Increasing pressure favours the side with fewer gas molecules (right, ammonia), so more ammonia will be made.