Carboxylic Acids (Cambridge O Level Chemistry)

• 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