Carboxylic acidsEdexcel A-Level Chemistry: Mind map

Exam questions on Carboxylic acids

1. Ethanoic acid (relative molecular mass 60.0, boiling temperature 118 °C) has a much higher boiling temperature than propanal (relative molecular mass 58.0, boiling temperature 49 °C). Ethanoic acid mixes with water in all proportions, but hexanoic acid, CH₃(CH₂)₄COOH, is only slightly soluble.
   Explain why ethanoic acid has a much higher boiling temperature than propanal.2 marks
2. A student plans to make propanoic acid in two different ways. One route starts from propan-1-ol. The other route starts from propanenitrile.
   State the colour change seen when propan-1-ol is oxidised to propanoic acid by acidified potassium dichromate(VI), and explain why the mixture must be heated under reflux.2 marks
3. Ethanoic acid is used as a starting material in several reactions. In one test, aqueous sodium carbonate is added to ethanoic acid. In other reactions, ethanoic acid is converted into an acyl chloride by phosphorus(V) chloride and into an ester by reaction with ethanol.
   Describe what is seen when aqueous sodium carbonate is added to ethanoic acid, and write the equation for the reaction.3 marks