A pilot plant carries out two runs in a closed test reactor. The same starting amounts of nitrogen and hydrogen and the same pressure are used in each run. The forward reaction that makes ammonia is exothermic. Run 1 uses an iron catalyst. In Run 2, one operating condition is changed. Each run is allowed to reach equilibrium.
| Run | Ammonia in the equilibrium mixture (%) |
|---|---|
| 1 | 18 |
| 2 | 31 |
What change was made in Run 2, and why did the percentage of ammonia increase?
The iron catalyst was removed, so the reverse reaction became slower than the forward reaction.
The temperature was decreased, so the equilibrium shifted towards ammonia.
The temperature was increased, so the faster reaction produced more ammonia at equilibrium.
More iron catalyst was added, so the equilibrium shifted towards ammonia.
71 exam-style questions on AQA GCSE Chemistry 10.4 The Haber process and the use of NPK fertilisers, covering 10.4.1a The Haber process, 10.4.1b Equilibrium and rate in the Haber process, and 10.4.2 Production and uses of NPK fertilisers. Each one has a worked solution and a mark scheme showing where the marks go.