# The production of ammonia in the Haber process involves the following reversible reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). The forward reaction is exothermic. A chemical engineer is considering changing the conditions used in the Haber process. Explain how increasing the temperature and increasing the pressure each affect the position of dynamic equilibrium in this reaction.

> OCR A-Level Chemistry A (H432) — 5.1 Rates, equilibrium and pH · Explain · 5 marks

> The Haber process is used industrially to manufacture ammonia. The reaction is carried out in a closed system, meaning the reaction reaches dynamic equilibrium.

## Mark scheme (5 marks)

1. Increasing temperature shifts the equilibrium position in the direction of the endothermic reaction
2. So increasing temperature shifts the equilibrium to the left / towards the reactants, producing less ammonia
3. Increasing pressure shifts the equilibrium position towards the side with the smaller number of moles of gas
4. The right-hand side has 2 moles of gas compared to 4 moles on the left, so equilibrium shifts to the right / towards the products
5. Both changes are explained by Le Chatelier's principle — the equilibrium position shifts to counteract the imposed change

## Key terms

- [dynamic equilibrium](https://www.gradenine.co.uk/glossary/dynamic-equilibrium)
- [reversible reaction](https://www.gradenine.co.uk/glossary/reversible-reaction)

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/the-production-of-ammonia-in-the-95cdfa43) · Published by Druglandscape Ltd.