# A student has a sample of propanal and a sample of propanone. She wants to confirm which sample is which using a chemical test. Describe how the student could use Fehling's solution to identify which sample is propanal, and explain the chemistry that allows this identification to be made.

> WJEC A-Level Chemistry (Wales) — 4.4 Aldehydes and ketones · Describe and Explain · 5 marks

## Mark scheme (5 marks)

1. Add Fehling's solution to each sample and warm/heat the mixture
2. The sample that produces a brick-red/orange-red precipitate is propanal
3. Propanone gives no colour change / remains blue with Fehling's solution
4. Propanal is an aldehyde and is oxidised by Fehling's solution / acts as a reducing agent
5. Propanone is a ketone and cannot be oxidised under these conditions / ketones do not react with Fehling's solution

## Key terms

- [Fehling's solution](https://www.gradenine.co.uk/glossary/fehling-s-solution)

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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/a-student-has-a-sample-of-17676ec0) · Published by Druglandscape Ltd.