# Ethanol can be produced industrially by the reversible reaction of ethene with steam. The reaction reaches dynamic equilibrium in a closed system. Explain how changing the conditions affects the position of equilibrium and the yield of ethanol, and describe what is meant by dynamic equilibrium in this context.

> Edexcel GCSE Chemistry (1CH0) — 5.3 Dynamic equilibria, calculations involving volumes of gases (Chem only) · Explain · 4 marks

> Ethene reacts with steam in a reversible reaction: C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g). The forward reaction is exothermic. The reaction is carried out in a closed system under high pressure.

## Mark scheme (4 marks)

1. At dynamic equilibrium, the rate of the forward reaction equals the rate of the backward reaction
2. At dynamic equilibrium, the concentrations of reactants and products remain constant
3. Increasing pressure shifts the equilibrium to the right / towards the products, increasing the yield of ethanol
4. Decreasing temperature shifts the equilibrium to the right / towards the products (because the forward reaction is exothermic), increasing the yield of ethanol

## Key terms

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

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