# Butanedioic acid is a dicarboxylic acid found in unripe fruit. It reacts with sodium carbonate solution. Describe what you would observe during this reaction and explain why butanedioic acid behaves in this way. Include in your answer the name of the gas produced and how you would confirm its identity.

> WJEC A-Level Chemistry (Wales) — 3.4 Carbonyls and acids · Describe · 5 marks

> Butanedioic acid is a dicarboxylic acid. Like all carboxylic acids, it reacts with sodium carbonate solution.

## Mark scheme (5 marks)

1. Effervescence / bubbles / fizzing is observed
2. The solid sodium carbonate dissolves / the solution fizzes and the solid disappears (or if solution stated, fizzing in solution is acceptable)
3. Carbon dioxide is the gas produced
4. Butanedioic acid reacts with sodium carbonate because it is an acid / it donates H⁺ ions / carboxylic acids react with carbonates to form a salt, water and carbon dioxide
5. To confirm the identity of the gas, bubble it through limewater — a positive result is that the limewater turns milky / cloudy

## Key terms

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

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/butanedioic-acid-is-a-dicarboxylic-acid-47f73e06) · Published by Druglandscape Ltd.