Carboxylic acids and derivativesAQA A-Level Chemistry: Topic test

20 questions, 54 marks

AQA A-Level Chemistry

Carboxylic acids and derivatives topic test

Total 54 marks

Name

Class

Date

1
Pentyl ethanoate, CH₃COO(CH₂)₄CH₃, has a banana-like smell and is used as a food flavouring. It can be made in the laboratory by heating an acid and an alcohol with a few drops of concentrated sulfuric acid.
(a)
Which acid and alcohol are heated together to make pentyl ethanoate?
[1 mark]
APentanoic acid and ethanol
BEthanoic acid and pentan-1-ol
CEthanoic acid and pentan-2-ol
DPentanoic acid and methanol
(b)
Pentyl ethanoate is heated under reflux with aqueous sodium hydroxide. Which products are formed?
[1 mark]
AEthanoic acid and sodium pentoxide
BSodium pentanoate and ethanol
CEthanoic acid and pentan-1-ol
DSodium ethanoate and pentan-1-ol
(c)
The yield of pentyl ethanoate from this reaction is always less than 100%. Explain why, and suggest one way to increase the yield.
[2 marks]
Total for question 1: 4 marks
2
Propanoic acid, CH₃CH₂COOH, is a weak acid used as a food preservative. A student adds 25.0 cm³ of propanoic acid of concentration 0.500 mol dm⁻³ to an excess of solid calcium carbonate. One mole of any gas occupies 24.0 dm³ under the conditions of the experiment.
(a)
What would the student observe?
[1 mark]
AEffervescence, with a colourless gas that turns limewater milky
BA silver mirror forms on the test tube
CThe solution turns from orange to green
DThere is no reaction because carboxylic acids are too weak to react with carbonates
(b)
Which statement explains why propanoic acid is described as a weak acid?
[1 mark]
AIts molecule contains no hydrogen atom that can be lost
BIt is completely ionised in aqueous solution
CIt is only partially ionised in aqueous solution
DIt does not react with carbonates
(c)
Write the equation for the reaction, using 2 moles of propanoic acid per mole of calcium carbonate, and calculate the volume of carbon dioxide, in cm³, produced.
[2 marks]
Total for question 2: 4 marks
3
Propyl methanoate, HCOOCH₂CH₂CH₃ (M_r = 88.0), is hydrolysed in two separate experiments. In experiment 1 it is heated under reflux with dilute sulfuric acid. In experiment 2 it is heated under reflux with an excess of aqueous sodium hydroxide. The relative atomic masses are H = 1.0, C = 12.0, O = 16.0 and Na = 23.0.
(a)
Name the organic products formed in each experiment and explain why experiment 2 gives a higher yield of products than experiment 1.
[3 marks]
(b)
In experiment 2, 8.80 g of propyl methanoate is hydrolysed and the yield of sodium methanoate (M_r = 68.0) is 80.0%. Calculate the mass of sodium methanoate obtained.
[4 marks]
Total for question 3: 7 marks
4
Butanoyl chloride, CH₃CH₂CH₂COCl, is a colourless liquid that fumes in moist air. A student reacts it separately with water, with ethanol and with methylamine, CH₃NH₂. In each reaction the same inorganic compound is produced or neutralised.
(a)
Name the organic product of each reaction and the inorganic compound produced, and outline the mechanism for the reaction with methylamine.
[6 marks]
(b)
Ethyl butanoate can also be made by heating butanoic acid with ethanol and a small amount of concentrated sulfuric acid. Evaluate the use of butanoyl chloride, rather than butanoic acid, to make ethyl butanoate.
[6 marks]
Total for question 4: 12 marks
5
Four organic compounds each have a relative molecular mass of 74.0: propanoic acid, CH₃CH₂COOH, ethyl methanoate, HCOOCH₂CH₃, methyl ethanoate, CH₃COOCH₃, and butan-1-ol, CH₃CH₂CH₂CH₂OH.
(a)
Which compound liberates carbon dioxide when added to aqueous sodium carbonate?
[1 mark]
AMethyl ethanoate
BEthyl methanoate
CPropanoic acid
DButan-1-ol
(b)
Which pair of compounds are esters?
[1 mark]
AMethyl ethanoate and ethyl methanoate
BPropanoic acid and methyl ethanoate
CPropanoic acid and butan-1-ol
DEthyl methanoate and butan-1-ol
(c)
Write an equation, using structural formulae, for the formation of ethyl methanoate from methanoic acid and ethanol, and state the catalyst used.
[2 marks]
Total for question 5: 4 marks
6
Ethanoic anhydride, (CH₃CO)₂O (M_r = 102.0), reacts with water and with primary amines. In one experiment, 5.10 g of ethanoic anhydride is added to an excess of ethylamine, CH₃CH₂NH₂, forming N-ethylethanamide, CH₃CONHCH₂CH₃ (M_r = 87.0), and ethanoic acid. The yield of N-ethylethanamide is 80.0%.
(a)
What is formed when ethanoic anhydride reacts with water?
[1 mark]
AEthanoic acid and hydrogen chloride
BEthanol and ethanoic acid
CEthanal and water
DTwo molecules of ethanoic acid
(b)
Which type of mechanism describes the reaction of ethanoic anhydride with ethylamine?
[1 mark]
AElectrophilic substitution
BNucleophilic addition-elimination
CFree-radical substitution
DElectrophilic addition
(c)
Calculate the mass of N-ethylethanamide obtained in the experiment.
[2 marks]
Total for question 6: 4 marks
7
A student prepares an organic solid by an acylation reaction. The crude solid melts over the range 118 to 126 °C. After recrystallisation the pure solid melts over the range 134 to 135 °C, and the data book value for the pure compound is 135 °C. The theoretical yield was 6.00 g and the student obtained 3.90 g of recrystallised product.
(a)
Describe how the student should recrystallise the crude solid.
[3 marks]
(b)
Explain what the melting point data show about the purity of the crude and recrystallised solids, and calculate the percentage yield of the recrystallised solid.
[4 marks]
Total for question 7: 7 marks
8
Ester Q has molecular formula C₅H₁₀O₂. Heating Q under reflux with dilute sulfuric acid gives two organic products, R and S. R has a branched carbon chain, a relative molecular mass of 88.0, and gives effervescence when added to sodium carbonate solution. S has a relative molecular mass of 32.0. The relative atomic masses are H = 1.0, C = 12.0 and O = 16.0.
(a)
Deduce the structures of R, S and Q. Show your reasoning and write an equation for the hydrolysis.
[6 marks]
(b)
The acyl chloride T, (CH₃)₂CHCOCl, can be made from R. T reacts with S to give Q, and with ethylamine to give a different organic product. Write an equation for the reaction of T with S, explain the advantage of making Q from T rather than from R, name the product with ethylamine, and outline the mechanism of that reaction.
[6 marks]
Total for question 8: 12 marks

End of questions

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).