# Tartaric acid (C₄H₆O₆) is a weak acid found in grapes and wine. Hydrochloric acid (HCl) is a strong acid. Both acids are dissolved in water to make solutions of equal concentration. Explain why the electrical conductivity of the tartaric acid solution is lower than that of the hydrochloric acid solution of the same concentration.

> Edexcel A-Level Chemistry (9CH0) — 12.1 Strong and weak acids · Explain · 5 marks

> Tartaric acid (C₄H₆O₆) is a weak acid found in grapes and wine. Hydrochloric acid (HCl) is a strong acid. Both acids are dissolved in water to make solutions of equal concentration.

## Mark scheme (5 marks)

1. Hydrochloric acid is fully/completely dissociates (ionises) in aqueous solution
2. Tartaric acid only partially dissociates (ionises) in aqueous solution
3. A reversible equilibrium is established for tartaric acid / the dissociation of tartaric acid is reversible
4. The tartaric acid solution contains fewer ions / a lower concentration of ions than the hydrochloric acid solution at the same concentration
5. Electrical conductivity depends on the number/concentration of ions present, so the lower ion concentration in tartaric acid gives lower conductivity

## Key terms

- [strong acid](https://www.gradenine.co.uk/glossary/strong-acid)
- [weak acid](https://www.gradenine.co.uk/glossary/weak-acid)
- [electrical conductivity](https://www.gradenine.co.uk/glossary/electrical-conductivity)
- [ions](https://www.gradenine.co.uk/glossary/ions)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "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/tartaric-acid-c-h-o-is-a-weak-881d71ff) · Published by Druglandscape Ltd.