# Ethanal and propanone are both carbonyl compounds. Describe how Tollens' reagent can be used to distinguish between ethanal and propanone, and explain the chemistry that accounts for the different results observed.

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

## Mark scheme (5 marks)

1. Tollens' reagent contains silver ions (Ag⁺) / is an ammoniacal silver nitrate solution
2. Ethanal (the aldehyde) produces a silver mirror on the test tube / a grey/silver precipitate forms with ethanal
3. Propanone (the ketone) gives no reaction / no silver mirror / solution remains colourless
4. Ethanal is oxidised (by the Tollens' reagent) / aldehydes are reducing agents that are oxidised to carboxylic acids (ethanoic acid)
5. The silver ions (Ag⁺) are reduced to silver metal (Ag), forming the silver mirror / ketones cannot be oxidised under these conditions so no reduction of silver ions occurs

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/ethanal-and-propanone-are-both-carbonyl-74fc65e4) · Published by Druglandscape Ltd.