# Ethanol can be produced by the hydration of ethene in a reversible reaction: C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g)   ΔH = −46 kJ/mol. The reaction is carried out at 300 °C and high pressure with a catalyst. Explain how changing the temperature and changing the pressure each affect the position of equilibrium and the yield of ethanol.

> AQA A-Level Chemistry (7405) — 3.1.6 Chemical equilibria, Le Chatelier and Kc · Explain · 5 marks

## Mark scheme (5 marks)

1. Increasing temperature shifts the equilibrium to the left (reverse reaction is favoured)
2. Because the forward reaction is exothermic, the system opposes the increase by favouring the endothermic (reverse) direction
3. Increasing temperature therefore decreases the yield of ethanol
4. Increasing pressure shifts the equilibrium to the right (towards the side with fewer moles of gas)
5. Increasing pressure therefore increases the yield of ethanol

## Key terms

- [position of equilibrium](https://www.gradenine.co.uk/glossary/position-of-equilibrium)
- [yield](https://www.gradenine.co.uk/glossary/yield)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](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/ethanol-can-be-produced-by-the-db7c62e4) · Published by Druglandscape Ltd.