# Ethanol can be manufactured by the hydration of ethene. The reaction is reversible and reaches a dynamic equilibrium in a closed container.

C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g)     ΔH = −46 kJ mol⁻¹

The equilibrium constant, Kc, for this reaction at 300 °C is 2.4 × 10⁻² mol⁻¹ dm³.

Explain what the value of Kc tells us about the position of equilibrium at 300 °C, and predict and explain what happens to the value of Kc when the temperature is increased.

> Eduqas A-Level Chemistry — 3.8 Equilibrium constants · Explain · 5 marks

## Mark scheme (5 marks)

1. Kc less than 1 indicates the equilibrium lies to the left / favours the reactants
2. The concentration of products is low compared to the concentration of reactants
3. Increasing temperature causes Kc to decrease
4. The reaction is exothermic, so increasing temperature favours the reverse/endothermic reaction
5. This means less ethanol (product) is present at equilibrium / equilibrium shifts further to the left

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](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-manufactured-by-the-76b6cd38) · Published by Druglandscape Ltd.