Carboxylic acids and estersAQA A-Level Chemistry: Subtopic test

1. 1
   A student adds a sample of ethanoic acid to aqueous sodium carbonate. In a separate experiment she warms ethanoic acid with ethanol and a few drops of concentrated sulfuric acid.

   (a)

   What is observed when ethanoic acid is added to aqueous sodium carbonate?

   [1 mark]

   • AThe mixture turns orange
   • BA silver mirror forms
   • CA white precipitate forms
   • DBubbles of gas are given off

   (b)

   What is the organic product of the second experiment?

   [1 mark]

   • AEthyl methanoate
   • BEthyl ethanoate
   • CEthanal
   • DDiethyl ether

   (c)

   Write the equation for the reaction of ethanoic acid with sodium carbonate.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Methyl butanoate has a fruity smell like apples and is used in food flavourings and perfumes. It is made in the laboratory from a carboxylic acid and an alcohol.

   (a)

   Which carboxylic acid and alcohol are used to make methyl butanoate?

   [1 mark]

   • AMethanoic acid and butan-1-ol
   • BButanoic acid and ethanol
   • CButanoic acid and methanol
   • DPropanoic acid and methanol

   (b)

   Which of these is a common use of esters?

   [1 mark]

   • AAs plasticisers and perfumes
   • BAs oxidising agents in bleach
   • CAs the acid catalyst in esterification
   • DAs electrolytes in batteries

   (c)

   Write the equation for the formation of methyl butanoate and name a suitable catalyst.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A company manufactures soap and biodiesel from vegetable oil. Vegetable oils and animal fats are esters of propane-1,2,3-triol with long-chain carboxylic acids.

   (a)

   Describe what happens when a vegetable oil is heated with aqueous sodium hydroxide, naming the products.

   [3 marks]

   (b)

   Describe how biodiesel is produced from vegetable oil and state what biodiesel consists of.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Esters can be hydrolysed in acidic or alkaline conditions. A student studies the hydrolysis of ethyl ethanoate, while a manufacturer hydrolyses the fat glyceryl tristearate, (C₁₇H₃₅COO)₃C₃H₅, with aqueous sodium hydroxide to make soap.

   (a)

   Compare the hydrolysis of ethyl ethanoate under acidic conditions with its hydrolysis under alkaline conditions. Include the reagents, the organic products and the extent of reaction.

   [6 marks]

   (b)

   Write an equation for the hydrolysis of glyceryl tristearate with aqueous sodium hydroxide and name the other product. The manufacturer hydrolyses 8.90 g of glyceryl tristearate (Mr = 890). Calculate the theoretical mass of sodium stearate, C₁₇H₃₅COONa (Mr = 306), formed. The manufacturer obtains 7.65 g of sodium stearate. Calculate the percentage yield.

   [6 marks]

   Total for question 4: 12 marks

End of questions