Chemistry · Oct / Nov 2021 · Paper 12 · Question 25

Ammonia is made by a reversible reaction. N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = –92 kJ / mol A chemist investigates how the percentage of ammonia at equilibrium changes with pressure. The experiment is carried out both at 250 °C and at 350 °C. Which graph shows the chemist’s results?

1. A% NH3 at equilibrium vs pressure; 350 °C curve above 250 °C curve
2. B% NH3 at equilibrium vs pressure; 250 °C curve above 350 °C curve
3. C% NH3 at equilibrium vs pressure; 350 °C curve above 250 °C curve, both decreasing
4. D% NH3 at equilibrium vs pressure; 250 °C curve above 350 °C curve, both decreasing

As printed in the paper