# The Contact Process is used in industry to produce sulfur trioxide, SO₃, which is needed to make sulfuric acid. One step in the Contact Process involves the following reversible reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). The forward reaction is exothermic. Explain how increasing the temperature affects the position of equilibrium and the yield of SO₃ in this reaction.

> OCR GCSE Chemistry A: Gateway Science (J248) — C5.3 Equilibria · Explain · 4 marks

> The Contact Process is a major industrial process used worldwide to manufacture sulfuric acid. A key reversible reaction in this process reaches dynamic equilibrium under carefully controlled conditions.

## Mark scheme (4 marks)

1. Increasing temperature shifts the equilibrium position in the direction of the endothermic reaction
2. The equilibrium shifts in the reverse/backward direction (because the forward reaction is exothermic, so the reverse is endothermic)
3. This is because the system acts to oppose / counteract the change (Le Chatelier's principle)
4. The yield of SO₃ decreases because less product is present at the new equilibrium position

## Key terms

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

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](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-contact-process-is-used-in-b0971ce9) · Published by Druglandscape Ltd.