# Diesel is a hydrocarbon fuel obtained from crude oil. When diesel undergoes incomplete combustion in a car engine, several pollutants are produced. Explain why incomplete combustion occurs in a car engine and describe the harmful effects of the pollutants formed.

> Edexcel A-Level Chemistry (9CH0) — 8.1 Enthalpy changes and Hess cycles · Explain · 5 marks

> Diesel engines are widely used in lorries and buses. Concerns have been raised about the air quality near busy roads, particularly in urban areas.

## Mark scheme (5 marks)

1. Incomplete combustion occurs because there is insufficient oxygen (supply) in the engine
2. Carbon monoxide is produced as a pollutant
3. Carbon monoxide is toxic / harmful to humans because it reduces the ability of blood to carry oxygen
4. Carbon particulates (soot) are also produced
5. Carbon particulates cause global dimming and/or health problems for humans

## Key terms

- [incomplete combustion](https://www.gradenine.co.uk/glossary/incomplete-combustion)
- [pollutants](https://www.gradenine.co.uk/glossary/pollutants)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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/diesel-is-a-hydrocarbon-fuel-obtained-905dce35) · Published by Druglandscape Ltd.