# Ethene and ethane are both hydrocarbons that can be produced from crude oil. Explain why ethene is described as an unsaturated hydrocarbon and state the general formula of the homologous series to which ethene belongs.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 4.4 Alkenes · Explain · 4 marks

> Ethene has the molecular formula C₂H₄. Ethane has the molecular formula C₂H₆.

## Mark scheme (4 marks)

1. Ethene contains a carbon–carbon double bond
2. Because of this double bond, ethene does not contain the maximum number of hydrogen atoms (it is not saturated with hydrogen)
3. The general formula of alkenes is CₙH₂ₙ
4. Ethene fits this general formula because with n = 2, the formula gives C₂H₄, which matches ethene's molecular formula

## Key terms

- [unsaturated](https://www.gradenine.co.uk/glossary/unsaturated)
- [general formula](https://www.gradenine.co.uk/glossary/general-formula)
- [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/ethene-and-ethane-are-both-hydrocarbons-0eb8a6d7) · Published by Druglandscape Ltd.