# The manufacture of methanol involves the reversible reaction: CO(g) + 2H₂(g) ⇌ CH₃OH(g). The forward reaction is exothermic. Industrial chemists must choose conditions carefully to maximise the yield of methanol. Explain how changing temperature and pressure affect the position of equilibrium in this reaction, and state the direction each change shifts the equilibrium.

> OCR A-Level Chemistry B: Salters (H433) — 5.1 Rates, equilibrium and pH · Explain · 5 marks

> Methanol is an important industrial solvent and fuel additive. It is produced from carbon monoxide and hydrogen gases in a closed system, allowing dynamic equilibrium to be established.

## Mark scheme (5 marks)

1. Increasing temperature shifts the equilibrium position towards the endothermic (backward/reverse) reaction
2. Because the system counteracts the change by absorbing the extra heat energy (Le Chatelier's principle)
3. Decreasing temperature shifts the equilibrium position towards the exothermic (forward) reaction, increasing methanol yield
4. Increasing pressure shifts the equilibrium towards the side with fewer moles of gas
5. The equilibrium shifts to the right (towards methanol) when pressure is increased, because the reactant side has 3 moles of gas and the product side has only 1 mole of gas

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/the-manufacture-of-methanol-involves-the-5472cae3) · Published by Druglandscape Ltd.