# Ethanol can be produced by the hydration of ethene. The reaction is reversible and reaches dynamic equilibrium in a closed system. The equation for the reaction is: C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g)   ΔH = −46 kJ/mol. Explain the effect on the position of equilibrium and on the yield of ethanol when the temperature is decreased and when the pressure is increased.

> Edexcel A-Level Chemistry (9CH0) — 10.1 Dynamic equilibria and Le Chatelier · Explain · 5 marks

> Ethanol can be produced industrially by reacting ethene with steam. The reaction is exothermic in the forward direction and reaches dynamic equilibrium in a closed system: C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g)   ΔH = −46 kJ/mol

## Mark scheme (5 marks)

1. Decreasing temperature shifts the equilibrium to the right (towards the products / in the forward direction)
2. Because the forward reaction is exothermic, so lowering temperature causes the equilibrium to shift in the direction that releases heat / opposes the change (Le Chatelier's principle)
3. Decreasing temperature increases the yield of ethanol
4. Increasing pressure shifts the equilibrium to the right (towards the products / in the forward direction)
5. Because there are fewer moles of gas on the right-hand side (2 moles of gas on the left, 1 mole on the right), so increasing pressure favours the side with fewer gas molecules, increasing the yield of ethanol

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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/ethanol-can-be-produced-by-the-8715e8cb) · Published by Druglandscape Ltd.