# Methanoic acid is a carboxylic acid found naturally in ant venom. Explain why methanoic acid is described as a weak acid, and describe what you would observe when a small piece of magnesium ribbon is added to a dilute solution of methanoic acid.

> Eduqas A-Level Chemistry — 4.5 Carboxylic acids and their derivatives · Explain · 5 marks

> Methanoic acid (HCOOH) is the simplest carboxylic acid. It is a weak acid with a sharp, pungent smell.

## Mark scheme (5 marks)

1. Methanoic acid only partially dissociates (ionises) in water
2. So the concentration of H⁺ ions in solution is low
3. Effervescence / bubbles are observed
4. The magnesium gradually dissolves / gets smaller
5. The reaction is slower / less vigorous than with a strong acid of the same concentration

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/methanoic-acid-is-a-carboxylic-acid-9a859432) · Published by Druglandscape Ltd.