# A reversible reaction takes place in a sealed container. Describe what happens to the concentrations of reactants and products from the start of the reaction until equilibrium is reached.

> AQA GCSE Chemistry (8462) — 4.6.2 Reversible reactions and dynamic equilibrium · Describe · 4 marks

## Mark scheme (4 marks)

1. The forward reaction converts reactants into products, so the concentration of reactants decreases
2. The concentration of products increases (as the forward reaction proceeds)
3. The reverse reaction also occurs / products react to re-form reactants
4. At equilibrium the concentrations of reactants and products remain constant because the forward and reverse reactions occur at exactly the same rate

## Key terms

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

## Related

- [Revision notes for AQA GCSE Chemistry (8462)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-reversible-reaction-takes-place-in-e0e73f89) · Published by Druglandscape Ltd.