# A student carries out a multi-step organic synthesis. In the first step, ethene reacts with steam to produce ethanol. In the second step, ethanol is oxidised to produce ethanoic acid. The student wants to confirm the identity of the ethanoic acid product using chemical tests. Describe the chemical tests the student could carry out to show that the product contains a carboxylic acid group, and state the observations that would confirm a positive result.

> WJEC A-Level Chemistry (Wales) — 4.8 Organic synthesis and analysis · Describe · 5 marks

> Ethanoic acid is a carboxylic acid commonly used in the food industry. It can be made in the laboratory from ethanol by oxidation.

## Mark scheme (5 marks)

1. Add the product to sodium carbonate (or sodium hydrogencarbonate) solution
2. Observation: effervescence / bubbles produced (carbon dioxide gas given off)
3. Pass the gas produced through limewater to confirm it is carbon dioxide
4. Test with litmus / universal indicator — the product turns blue litmus red / gives an acidic pH
5. State that both tests together confirm the presence of a carboxylic acid (acidic AND produces CO₂ with carbonate)

## Key terms

- [carboxylic acid](https://www.gradenine.co.uk/glossary/carboxylic-acid)

## Related

- [Revision notes for WJEC A-Level Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-carries-out-a-multi-step-c273aa5d) · Published by Druglandscape Ltd.