# Nitrogen monoxide, NO, is produced as a by-product during combustion reactions in car engines. It can be removed by the following reversible reaction in a catalytic converter: 2CO(g) + 2NO(g) ⇌ 2CO₂(g) + N₂(g). Explain what is meant by dynamic equilibrium and describe the conditions under which this reversible reaction would reach dynamic equilibrium in a catalytic converter.

> Edexcel GCSE Chemistry (1CH0) — 5.3 Dynamic equilibria, calculations involving volumes of gases (Chem only) · Explain · 4 marks

> Catalytic converters in cars use reversible reactions to reduce harmful exhaust emissions. One such reaction involves carbon monoxide reacting with nitrogen monoxide.

## Mark scheme (4 marks)

1. Dynamic equilibrium is reached when the rate of the forward reaction equals the rate of the backward/reverse reaction
2. The concentrations of reactants (CO and NO) and products (CO₂ and N₂) remain constant at dynamic equilibrium
3. The system must be closed/sealed so that no reactants or products can escape
4. Both the forward reaction and backward/reverse reaction continue to occur simultaneously at dynamic equilibrium

## Key terms

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

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- [Revision notes for Edexcel GCSE Chemistry (1CH0)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/nitrogen-monoxide-no-is-produced-as-ecb67e8e) · Published by Druglandscape Ltd.