# The reaction between sulfur dioxide and oxygen is a reversible reaction, as shown: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). The forward reaction is exothermic. A chemical engineer suggests increasing the temperature of the reaction vessel once dynamic equilibrium has been reached. Explain the effect this change has on the position of equilibrium and on the concentrations of SO₂ and SO₃.

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

## Mark scheme (4 marks)

1. An increase in temperature shifts the equilibrium position in the direction of the endothermic reaction
2. The backward/reverse reaction is the endothermic reaction, so equilibrium shifts to the left / in the reverse direction
3. The concentration of SO₂ increases
4. The concentration of SO₃ decreases

## Key terms

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

## 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)
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Source: [GradeNine](https://www.gradenine.co.uk/q/the-reaction-between-sulfur-dioxide-and-d83e1baf) · Published by Druglandscape Ltd.