# A sealed flask contains the following reversible reaction at dynamic equilibrium: H₂(g) + I₂(g) ⇌ 2HI(g). The temperature of the flask is then increased. Explain what is meant by the term 'dynamic equilibrium' and describe what happens to the equilibrium position when the temperature is increased, given that the forward reaction is exothermic.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 3.3 Reversible reactions and equilibria · Explain · 4 marks

## Mark scheme (4 marks)

1. At dynamic equilibrium the rate of the forward reaction equals the rate of the backward reaction
2. The concentrations of reactants and products remain constant (at dynamic equilibrium)
3. Increasing temperature shifts the equilibrium position in the direction of the endothermic reaction
4. The yield of HI decreases / the concentration of HI decreases (because the backward/reverse reaction is favoured)

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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/a-sealed-flask-contains-the-following-1b0d865f) · Published by Druglandscape Ltd.