# Nitrogen dioxide, NO₂, and dinitrogen tetroxide, N₂O₄, exist in a reversible reaction in a sealed container: 2NO₂(g) ⇌ N₂O₄(g). The forward reaction is exothermic. Explain what happens to the position of equilibrium when the temperature of the sealed container is increased.

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

> Nitrogen dioxide (NO₂) is a brown gas and dinitrogen tetroxide (N₂O₄) is a colourless gas. They interconvert in a reversible reaction inside a sealed container, eventually reaching dynamic equilibrium.

## Mark scheme (4 marks)

1. The equilibrium position shifts to the left / towards the reactants / towards NO₂
2. Because increasing temperature favours the endothermic reaction / direction
3. This is because the system acts to counteract / oppose the change (Le Chatelier's principle)
4. The concentration of NO₂ increases and the concentration of N₂O₄ decreases (but both remain constant once the new equilibrium is reached)

## 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/nitrogen-dioxide-no-and-dinitrogen-tetroxide-5b134715) · Published by Druglandscape Ltd.