# Aldehydes and ketones are both carbonyl compounds. Explain how you could use Tollens' reagent to distinguish between an aldehyde and a ketone, and explain why the test gives different results for each compound class.

> Edexcel A-Level Chemistry (9CH0) — 17.2 Aldehydes and ketones · Explain · 5 marks

> Tollens' reagent contains silver ions in aqueous ammonia solution. It is used to distinguish between aldehydes and ketones.

## Mark scheme (5 marks)

1. Aldehydes give a positive result with Tollens' reagent / silver mirror forms on the inside of the tube with an aldehyde
2. Ketones give a negative result / no silver mirror / no change observed with Tollens' reagent
3. Aldehydes are oxidised (by the Tollens' reagent) / aldehyde acts as a reducing agent
4. Silver ions (Ag⁺) are reduced to silver metal (Ag) by the aldehyde
5. Ketones cannot be oxidised under these mild conditions / ketones do not have the C–H bond on the carbonyl carbon and so cannot act as reducing agents

## Key terms

- [aldehyde](https://www.gradenine.co.uk/glossary/aldehyde)
- [ketone](https://www.gradenine.co.uk/glossary/ketone)
- [Tollens' reagent](https://www.gradenine.co.uk/glossary/tollens-reagent)
- [carbonyl](https://www.gradenine.co.uk/glossary/carbonyl)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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/aldehydes-and-ketones-are-both-carbonyl-77d4d8dd) · Published by Druglandscape Ltd.