Practise 29 real questions on Halogen compounds from 2021 to 2026. See the answer and explanation as soon as you answer.
Halogen compounds is one of the 18 main topics in our A Level Chemistry (Cambridge (CAIE) 9701) question bank, and about 4% of its real questions come from it. Tayyari Karo has 29 real questions on this topic from 2021 to 2026, from Paper 1, Paper 2, Paper 4; 26 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 15 medium, 12 hard, 2 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
A sample of 2-bromobutane is strongly heated in a concentrated ethanolic solution of sodium hydroxide. How many isomeric organic products are formed (structural isomerism and stereoisomerism taken into account)?
Answer: C. 3
Elimination gives but-1-ene, cis-but-2-ene and trans-but-2-ene: 3 isomers.
Two reactions, both with NaOH(aq) in excess under the same conditions: 1 2-bromo-2-methylbutane heated with NaOH(aq); 2 2-chloro-2-methylbutane heated with NaOH(aq). 30.18 g of 2-bromo-2-methylbutane (Mr 150.9) forms 12.32 g of product X (the tertiary alcohol, Mr 88.15). Which row is correct (percentage yield of X; relative rate of reaction)?
Answer: C. 70%; 1 is faster than 2
Moles bromide = 30.18/150.9 = 0.200 mol, theoretical moles of alcohol X = 0.200 mol (mass 17.63 g); actual yield 12.32 g gives % yield = 12.32/17.63 × 100 ≈ 70%. The C-Br bond is weaker than C-Cl, so the bromoalkane (reaction 1) reacts faster by SN1 hydrolysis.
2-bromopropane is converted to 1,2-dibromopropane in a pathway involving two reactions: 2-bromopropane → compound X (reaction 1) → 1,2-dibromopropane (reaction 2). What are the reagents and conditions for the two reactions?
Answer: D. Reaction 1: heat under reflux with ethanolic NaOH; Reaction 2: Br2(l) at room temperature
Ethanolic NaOH under reflux eliminates HBr from 2-bromopropane to give propene (X); propene then undergoes electrophilic addition with liquid Br2 at room temperature to give 1,2-dibromopropane.
Which row describes the solvent used and type of reaction occurring when bromoethane reacts with NaOH to form ethene?
Answer: A. ethanol, elimination
Ethene is formed from bromoethane + NaOH dissolved in ethanol (not water) via an elimination reaction (heat, OH⁻ acting as a base).
Ethanol can be used to make propanenitrile in two steps: CH3CH2OH →(X) CH3CH2Br →(Y) CH3CH2CN. What types of reaction are X and Y?
Answer: C. nucleophilic substitution; nucleophilic substitution
Ethanol to bromoethane (e.g. with HBr or PBr3/NaBr+H2SO4) is nucleophilic substitution (Br⁻ attacks the polar C-OH carbon after protonation, or a similar mechanism); bromoethane to propanenitrile (with KCN) is also nucleophilic substitution (CN⁻ attacks the polar C-Br carbon).
Which statements are correct? 1: 1,1-difluoroethane is less reactive than 1,1-dichloroethane. 2: 1,1-difluoroethane is polar. 3: The C–F bond is stronger than the C–Cl bond.
Answer: A. 1, 2 and 3 are correct
The C–F bond (≈485 kJ mol⁻¹) is stronger than C–Cl (≈340 kJ mol⁻¹), making fluoroalkanes less reactive than chloroalkanes; 1,1-difluoroethane's C–F bonds are highly polar and the molecule's shape does not cancel this, so it is polar — all three correct.
| Session | Paper 1 | Paper 2 | Paper 4 |
|---|---|---|---|
| May/June 2026 | 2 | – | – |
| May/June 2025 | 3 | – | – |
| October/November 2025 | 2 | 1 | – |
| May/June 2024 | 3 | – | – |
| October/November 2024 | 3 | – | – |
| May/June 2023 | 2 | – | – |
| October/November 2023 | 1 | – | 1 |
| May/June 2022 | 3 | – | 1 |
| October/November 2022 | 1 | – | – |
| May/June 2021 | 2 | – | – |
| October/November 2021 | 4 | – | – |
29 real A Level Chemistry (9701) questions on Halogen compounds from 2021 to 2026, from Paper 1, Paper 2, Paper 4. Each one shows the year, session and paper it came from.
Yes. Every question shows the correct answer and a short explanation the moment you answer.
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