Carboxylic Acids as Acids (AQA GCSE Chemistry)

Higher tier only

• 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 equilibrium 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 characteristic reactions, those reactions will be slow or even barely noticeable at room temperature