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Carboxylic acidsEdexcel International A Level Chemistry: Flashcards

What these 13 flashcards ask

  • What is the functional group of a carboxylic acid and its name ending?
  • Why do carboxylic acids have high boiling temperatures?
  • Why are short-chain carboxylic acids soluble in water?
  • Why does solubility fall as the chain lengthens?
  • How is a primary alcohol oxidised to a carboxylic acid?
  • Why is reflux, not distillation, used to make the acid?
  • Write the equation for hydrolysis of ethanenitrile with dilute HCl.
  • What is seen when a carboxylic acid is added to sodium carbonate?
  • Write the equation for ethanoic acid with sodium hydroxide.
  • What does PCl₅ do to a carboxylic acid?
  • What are the conditions for making an ester from an acid and an alcohol?
  • What does LiAlH₄ in dry ether do to a carboxylic acid?
  • Name the ester made from propanoic acid and methanol.

Exam questions on Carboxylic acids

  1. Ethanoic acid (Mr 60) boils at 118 °C, whereas propan-1-ol (Mr 60) boils at 97 °C and propanal (Mr 58) boils at 49 °C. Ethanoic acid is fully miscible with water.
    Explain why the solubility of carboxylic acids in water decreases as the length of the carbon chain increases.2 marks
  2. A chemist prepares ethanoic acid by two different routes. In the first, ethanol is heated under reflux with an excess of acidified potassium dichromate(VI). In the second, ethanenitrile is heated under reflux with dilute hydrochloric acid.
    Write a balanced equation for the hydrolysis of ethanenitrile by dilute hydrochloric acid.2 marks
  3. Propanoic acid is reacted separately with (i) aqueous sodium carbonate, (ii) phosphorus(V) chloride, (iii) ethanol with a few drops of concentrated sulfuric acid, heated under reflux, and (iv) lithium tetrahydridoaluminate(III) in dry ether.
    Describe what is seen in reaction (i) and name the organic product of reaction (ii). Write a balanced equation for reaction (i).3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).