# Decane (C₁₀H₂₂) is a hydrocarbon found in crude oil. When decane burns incompletely, carbon monoxide and water are produced instead of carbon dioxide and water. Explain why incomplete combustion occurs and describe two differences between the products of complete combustion and incomplete combustion of decane.

> Eduqas A-Level Chemistry — 3.2 Hydrocarbons · Explain · 5 marks

> Hydrocarbons are compounds that contain hydrogen and carbon only. They are found in crude oil and are widely used as fuels. The combustion of hydrocarbons can be complete or incomplete depending on the conditions.

## Mark scheme (5 marks)

1. Incomplete combustion occurs when there is insufficient/limited oxygen supply
2. Complete combustion produces carbon dioxide; incomplete combustion produces carbon monoxide (instead)
3. Carbon monoxide is toxic / poisonous whereas carbon dioxide is not (toxic)
4. Incomplete combustion releases less energy than complete combustion
5. Carbon (soot/particles) may also be produced during incomplete combustion but not during complete combustion

## Key terms

- [hydrocarbon](https://www.gradenine.co.uk/glossary/hydrocarbon)
- [complete combustion](https://www.gradenine.co.uk/glossary/complete-combustion)
- [incomplete combustion](https://www.gradenine.co.uk/glossary/incomplete-combustion)
- [carbon monoxide](https://www.gradenine.co.uk/glossary/carbon-monoxide)
- [carbon dioxide](https://www.gradenine.co.uk/glossary/carbon-dioxide)

## Related

- [Revision notes for Eduqas A-Level Chemistry](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/decane-c-h-is-a-hydrocarbon-found-701fcb6b) · Published by Druglandscape Ltd.