AQA GCSE Chemistry

Revision Notes

7.2.6 Carboxylic Acids as Acids

Higher Tier Only

Carboxylic Acids as Acids

  • Previously we have seen that carboxylic acids show all the typical reactions associated with acids
  • However, they differ from other ‘mineral’ acids ( hydrochloric, sulfuric and nitric) in the extent and vigour of their reactions
  • You should recall that acids release hydrogen ions in water giving their characteristic properties

HCl H++ Cl

  • Carboxylic acids dissolve in water, but they only partially ionise producing weakly acidic solutions with pH values of between 3 and 7
  • Carboxylic acids form an equilbrium with their ions, but most of the carboxylic acid molecules are undissociated

CH3COOH H+ + CH3COO

  • Ethanoic acid, for example, is around 95% undissociated
  • This means out of 100 molecules only about 5 actually ionise
  • The result is that, although they do show the characterstic reactions, those reactions will be slow or even barely noticeable at room temperature

Exam Tip

Although acidic, the carboxylic acids are weak as they don’t dissociate fully in water, so form aqueous solutions with a higher pH than that of strong acids such as HCl.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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