# Methanol, ethanol and propanol are all members of the alcohol homologous series. A chemist is investigating the combustion of these three alcohols and notices that as the carbon chain length increases, the flame produced becomes increasingly smoky and luminous. Explain why alcohols burn in air and describe how the products of complete combustion of ethanol differ from those of incomplete combustion.

> OCR A-Level Chemistry A (H432) — 4.2 Alcohols, haloalkanes and analysis · Explain · 5 marks

> Alcohols are widely used as fuels. Ethanol has the molecular formula C₂H₅OH. Complete combustion requires a plentiful supply of oxygen, whereas incomplete combustion occurs when oxygen is limited.

## Mark scheme (5 marks)

1. Alcohols contain carbon and hydrogen (and oxygen), so they can burn / react with oxygen
2. Complete combustion of ethanol produces carbon dioxide
3. Complete combustion of ethanol produces water
4. Incomplete combustion produces carbon monoxide instead of (or as well as) carbon dioxide
5. Incomplete combustion also produces carbon (soot / particles) / the flame is smokier because carbon particles are released

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](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/methanol-ethanol-and-propanol-are-all-0fe65056) · Published by Druglandscape Ltd.