CAIE A Level 9701

Chemistry 2020 · Oct/Nov

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9 Questions Q&A Available
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This CAIE A Level Chemistry paper focuses strongly on organic chemistry, especially aromatic compounds and polymers. Students can expect structured questions that test reaction mechanisms, reagent choice, equations, product naming, and explanations of chemical behaviour, rather than heavy calculation.…

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Questions & Model Answers 9 Qs

Q1bii
Short Answer 1 mark
State the name of the mechanism in (b)(i).
Electrophilic substitution
This is the mechanism used for nitration of benzene/phenyl compounds in the presence of NO2+.
Q1biii
Structured 2 marks
Identify the reagents needed to produce NO2+ ions. Write an equation to explain how these reagents produce NO2+ ions.
Concentrated sulfuric acid and concentrated nitric acid; HNO3 + H2SO4 -> NO2+ + HSO4- + H2O
Concentrated sulfuric acid protonates nitric acid, leading to formation of the nitronium ion.
Q1biv
Short Answer 2 marks
Give reagents and conditions for the production of phenylamine from nitrobenzene in step 2.
Sn and concentrated HCl, heat under reflux; then add NaOH to liberate phenylamine
Nitrobenzene is reduced to phenylamine using tin and hydrochloric acid, followed by alkali to free the amine.
Q1c i
Short Answer 1 mark
Phenylamine reacts with Br2(aq). Write an equation for this reaction. You may use structural or displayed formulae.
C6H5NH2 + 3Br2 -> C6H2Br3NH2 + 3HBr
Phenylamine undergoes rapid bromination to form 2,4,6-tribromophenylamine.
Q1c ii
Short Answer 1 mark
Name the organic product of this reaction.
2,4,6-tribromophenylamine
The amino group strongly activates the ring, directing substitution to the 2, 4 and 6 positions.
Q1c iii
Short Answer 1 mark
Describe two observations that can be seen when phenylamine reacts with Br2(aq).
Bromine water is decolourised; a white precipitate forms.
Phenylamine reacts readily with bromine water, removing its colour and producing insoluble tribromophenylamine.
Q1d
Structured 3 marks
Describe the relative basicities of ammonia, ethylamine and phenylamine, starting with the least basic. Explain your answer in terms of their structures.
Phenylamine < ammonia < ethylamine
In phenylamine, the lone pair on nitrogen is delocalised into the benzene ring, making it less available to accept H+. Ammonia has a lone pair available for protonation. Ethylamine is most basic because the ethyl group has a +I effect, increasing electron density on nitrogen and making the lone pair more available.
Q1e i
Short Answer 1 mark
1,3-diaminopropane, H2NCH2CH2CH2NH2, can be used to make polyamides. Identify one compound that would react with 1,3-diaminopropane to form a polyamide.
A dicarboxylic acid or diacyl chloride, for example hexanedioic acid or hexanedioyl dichloride.
Polyamides are formed by condensation between a diamine and a compound with two reactive carboxyl groups or acyl chloride groups.
Q1e ii
Structured 2 marks
Draw a section of the polymer chain formed from 1,3-diaminopropane and the compound you chose in (e)(i). Your answer should include four monomer residues (two of each type of monomer), show the amide link fully displayed, and clearly identify one repeat unit of this polymer.
A correct polyamide section showing alternating 1,3-diaminopropane and the chosen dicarboxylic acid/diacyl chloride residues linked by amide bonds, with one repeat unit identified.
The polymer must show condensation links of the form -CONH- between the diamine and the dicarboxylic acid/diacyl chloride residues.
Paper Details
Board CAIE
Level A Level
Subject Chemistry
Code 9701
Year 2020
Session Oct/Nov
Q&A 9 questions
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