# Ethanol and ethanoic acid react together in a closed system to form ethyl ethanoate and water. The equation for this reaction is: C₂H₅OH + CH₃COOH ⇌ CH₃COOC₂H₅ + H₂O. At a certain temperature, the equilibrium concentrations are: [C₂H₅OH] = 0.50 mol/dm³, [CH₃COOH] = 0.50 mol/dm³, [CH₃COOC₂H₅] = 1.50 mol/dm³, [H₂O] = 1.50 mol/dm³. Write the expression for the equilibrium constant, Kc, for this reaction, calculate its value, and state what a Kc value greater than 1 tells you about the position of equilibrium.

> WJEC A-Level Chemistry (Wales) — 3.8 Equilibrium constants · State · 5 marks

> Ethanol and ethanoic acid react in a closed system. At equilibrium, ethyl ethanoate and water are both present at a concentration of 1.50 mol/dm³, while ethanol and ethanoic acid are both present at a concentration of 0.50 mol/dm³.

## Mark scheme (5 marks)

1. Correct Kc expression: Kc = [CH₃COOC₂H₅][H₂O] / [C₂H₅OH][CH₃COOH]
2. Correct substitution of values into the Kc expression: (1.50 × 1.50) / (0.50 × 0.50)
3. Correct numerical value of Kc = 9 (no units required for this expression)
4. A Kc value greater than 1 means the products are favoured at equilibrium
5. A Kc value greater than 1 means the concentration of products is greater than the concentration of reactants at equilibrium

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "State" 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-and-ethanoic-acid-react-together-e8aa33c7) · Published by Druglandscape Ltd.