# Aldehydes and ketones are two families of organic compounds that contain the carbonyl group. Explain how the structure of an aldehyde differs from that of a ketone, name a chemical test that distinguishes between them, and state the result you would observe with each compound.

> Eduqas A-Level Chemistry — 4.4 Aldehydes and ketones · Explain · 5 marks

## Mark scheme (5 marks)

1. In an aldehyde, the carbonyl group (C=O) is at the end of the carbon chain (bonded to at least one hydrogen)
2. In a ketone, the carbonyl group (C=O) is in the middle of the carbon chain (bonded to two carbon atoms on either side)
3. Names Tollens' reagent (silver mirror test / ammoniacal silver nitrate) OR Fehling's solution OR Benedict's solution as a suitable distinguishing test
4. Correct positive result with the aldehyde — silver mirror forms (Tollens') OR brick-red/orange precipitate forms (Fehling's/Benedict's)
5. Correct negative result with the ketone — no change / no precipitate / no silver mirror formed

## Key terms

- [aldehyde](https://www.gradenine.co.uk/glossary/aldehyde)
- [ketone](https://www.gradenine.co.uk/glossary/ketone)
- [carbonyl group](https://www.gradenine.co.uk/glossary/carbonyl-group)

## 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)
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Source: [GradeNine](https://www.gradenine.co.uk/q/aldehydes-and-ketones-are-two-families-0b472d6f) · Published by Druglandscape Ltd.