AS Level · Chemistry 9701 · Organic chemistry

Hydrocarbons: AS Level Chemistry questions with answers

Free Hydrocarbons questions for AS Level Chemistry (9701), part of Organic chemistry. Each question has the answer and the marking points an examiner would look for.

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Hydrocarbons practice questions

Question 1Multiple choice · 1 markA* challenge

Propene reacts separately with cold dilute acidified KMnO4 and with hot concentrated acidified KMnO4.
Which row shows the organic products?

cold, dilutehot, concentrated
Apropane-1,2-diolan alcohol
Bpropane-1,2-diolethanoic acid and carbon dioxide
Can alkaneethanoic acid and carbon dioxide
Dethanoic acid and carbon dioxidepropane-1,2-diol
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Answer: B

Question 2Multiple choice · 1 mark

Which statement describes electrophile?

  1. A The enthalpy change for a reaction is independent of the route taken
  2. B A species with an unpaired electron
  3. C An electron-pair acceptor
  4. D The e.m.f. of a half-cell relative to the standard hydrogen electrode
Show answer

Answer: C

Question 3Multiple choice · 1 markA* challenge

Propene reacts with HBr.
What is the major product and the type of reaction?

major productmechanism
A2-bromopropaneelectrophilic addition
B2-bromopropanenucleophilic addition
C1-bromopropaneelectrophilic addition
D1-bromopropanefree-radical substitution
Show answer

Answer: A

Question 4Structured · 6 marksA* challenge

Alkanes react with chlorine in ultraviolet light.

(a)

Describe the mechanism of the reaction of methane with chlorine, naming each step.

[5]
(b)

Explain why a mixture of products is formed.

[1]
Show answers and mark scheme
PartAnswer and marking pointsMarks
(a)initiation, propagation, termination
initiation: Cl₂ → 2Cl• B1
propagation: CH₄ + Cl• → CH₃• + HCl B1
CH₃• + Cl₂ → CH₃Cl + Cl• B1
termination: two radicals combine B1
e.g. CH₃• + Cl• → CH₃Cl B1
5
(b)further substitution
further substitution of hydrogen atoms (e.g. CH₂Cl₂) B1
1
Question 5Structured · 4 marks

Alkenes undergo electrophilic addition.

Describe the mechanism for the reaction of ethene with bromine.

[4]
Show answers and mark scheme
PartAnswer and marking pointsMarks
induced dipole; carbocation; bromide attacks
Br₂ polarised by π electrons B1
curly arrow from C=C to Br B1
carbocation intermediate B1
Br⁻ attacks carbocation B1
4
Question 6Structured · 8 marksA* challenge

Methane reacts with chlorine in ultraviolet light.

(a)

Give equations for the initiation, two propagation steps and one termination step.

[4]
(b)

Explain why a mixture of products forms.

[1]
(c)

Propene reacts with HBr. Identify the major product and explain why it is formed.

[3]
Show answers and mark scheme
PartAnswer and marking pointsMarks
(a)Cl₂ → 2Cl•; CH₄ + Cl• → CH₃• + HCl; CH₃• + Cl₂ → CH₃Cl + Cl•; termination
Cl₂ → 2Cl• B1
CH₄ + Cl• → CH₃• + HCl B1
CH₃• + Cl₂ → CH₃Cl + Cl• B1
e.g. CH₃• + Cl• → CH₃Cl B1
4
(b)further substitution
Cl• can substitute further hydrogen atoms in CH₃Cl etc. B1
1
(c)2-bromopropane via secondary carbocation
2-bromopropane B1
formed from the secondary carbocation M1
which is more stable due to the positive inductive effect of two alkyl groups M1
3

More Organic chemistry questions

Introduction to organic chemistryHalogen compoundsHydroxy compoundsCarbonyl compoundsCarboxylic acids & derivativesNitrogen compoundsPolymerisationOrganic synthesisAnalytical techniques

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Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in