# A student tests two unknown organic compounds, Compound A and Compound B, using Fehling's solution. Compound A produces a brick-red precipitate when warmed with Fehling's solution. Compound B produces no colour change when warmed with Fehling's solution. Both compounds contain only carbon, hydrogen, and oxygen, and both contain a carbonyl group. Describe what these results tell the student about the identity of each compound, and explain why Fehling's solution gives different results with the two compounds.

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

## Mark scheme (5 marks)

1. Compound A is an aldehyde
2. Compound B is a ketone
3. Aldehydes can be oxidised (are reducing agents) / aldehydes reduce Fehling's solution
4. Ketones cannot be oxidised (are not reducing agents) / ketones do not reduce Fehling's solution
5. The brick-red precipitate is copper(I) oxide, formed when copper(II) ions in Fehling's solution are reduced

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-tests-two-unknown-organic-01eca416) · Published by Druglandscape Ltd.