Carboxylic Acids (Cambridge (CIE) O Level Chemistry): Revision Note

Carboxylic Acids

• The carboxylic acids behave like other acids

• They react with:

  • metals to form a salt and hydrogen

  • carbonates to form a salt, water and carbon dioxide gas

• They also  take part in neutralisation reactions to produce salt and water

• Ethanoic acid (also called acetic acid) is the acid used to make vinegar, which contains around 5% by volume of ethanoic acid

• The salts formed by the reaction of carboxylic acids all end –anoate

• So methanoic acid forms a salt called methanoate, ethanoic a salt called ethanoate etc.

• In the reaction with metals, a metal salt and hydrogen gas are produced

Example reactions of carboxylic acids 

• The reaction of ethanoic acid with magnesium forms the salt magnesium ethanoate and hydrogen gas: 

2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂

• In the reaction with hydroxides, salt and water are formed in a neutralisation reaction

• For example, the reaction between potassium hydroxide and propanoic acid forms the salt potassium propanoate and water: 

CH₃CH₂COOH + KOH → CH₃CH₂COOK + H₂O

• In the reaction with carbonates a metal salt, water and carbon dioxide gas are produced

• For example, in the reaction between potassium carbonate and butanoic acid, the salt potassium butanoate is formed with water and carbon dioxide

2CH₃CH₂CH₂COOH + K₂CO₃ → 2CH₃CH₂CH₂COOK + H₂O + CO₂