# Propene and butene are both members of the alkene homologous series. Explain why propene is classified as an unsaturated hydrocarbon, and state the empirical formula and general formula of the alkene homologous series.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.1 Introduction · Explain · 4 marks

## Mark scheme (4 marks)

1. Propene contains a carbon-to-carbon double bond
2. The presence of the double bond means propene is unsaturated (not all bonds are single bonds / not the maximum number of hydrogen atoms)
3. Empirical formula of alkenes is CH₂
4. General formula of alkenes is CₙH₂ₙ

## Key terms

- [unsaturated](https://www.gradenine.co.uk/glossary/unsaturated)
- [empirical formula](https://www.gradenine.co.uk/glossary/empirical-formula)
- [general formula](https://www.gradenine.co.uk/glossary/general-formula)
- [alkene](https://www.gradenine.co.uk/glossary/alkene)
- [homologous series](https://www.gradenine.co.uk/glossary/homologous-series)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](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/propene-and-butene-are-both-members-ca883c91) · Published by Druglandscape Ltd.