A Level Chemistry (A2) chapter 9: Halogen compounds MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
24 exam-style questions on Halogen compounds, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Which equation shows how the electrophile is formed when benzene is brominated using bromine and AlBr3?
A
Br2 + AlBr3 → Br+ + AlBr4−
B
Br2 + AlBr3 → Br− + AlBr4+
C
Br2 → 2Br•
D
Br2 + AlBr3 → 2Br+ + AlBr32−
Show answer
Answer: A. AlBr3 is a Lewis acid: it accepts Br− to become AlBr4−, leaving the electrophile Br+. Br2 → 2Br• is homolytic fission, which happens in ultraviolet light and leads to side-chain substitution instead.
2. Chloroethane and chlorobenzene are warmed separately with NaOH(aq). Each mixture is then acidified with dilute nitric acid and aqueous silver nitrate is added. What is observed?
A
a white precipitate forms only with the chloroethane mixture
B
a white precipitate forms only with the chlorobenzene mixture
C
a white precipitate forms with both mixtures
D
a cream precipitate forms with both mixtures
Show answer
Answer: A. Chloroethane is hydrolysed, releasing Cl− ions that give white AgCl. The C–Cl bond in chlorobenzene is not hydrolysed under these conditions, so no chloride ions are released.
3. Methylbenzene reacts with chlorine in the presence of AlCl3, and one chlorine atom is substituted. Which two isomers are the main products?
A
2-chloromethylbenzene and 3-chloromethylbenzene
B
3-chloromethylbenzene and 4-chloromethylbenzene
C
2-chloromethylbenzene and 4-chloromethylbenzene
D
(chloromethyl)benzene and 3-chloromethylbenzene
Show answer
Answer: C. The methyl group directs electrophiles to the 2- and 4-positions of the ring. (Chloromethyl)benzene, C6H5CH2Cl, is formed only under free-radical conditions (UV light).
4. 4-bromo(chloromethyl)benzene, BrC6H4CH2Cl, is heated with excess ammonia in ethanol in a sealed tube. What is the main organic product?
A
H2NC6H4CH2NH2
B
H2NC6H4CH2Cl
C
BrC6H4CH2NH2
D
BrC6H4CH2OH
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Answer: C. The Cl on the CH2 side chain behaves like a halogenoalkane and is substituted by NH2; the Br on the ring is not substituted. An –OH product would need aqueous hydroxide, not ammonia.
5. Equal amounts of chloroethane, bromoethane and chlorobenzene are warmed separately with aqueous silver nitrate in ethanol. What is the order in which a precipitate appears, fastest first?
A
chloroethane, bromoethane, chlorobenzene
B
chlorobenzene, chloroethane, bromoethane
C
bromoethane, chlorobenzene, chloroethane
D
bromoethane, chloroethane; no precipitate with chlorobenzene
Show answer
Answer: D. The C–Br bond is weaker than C–Cl, so bromoethane hydrolyses fastest (cream AgBr), then chloroethane (white AgCl). Chlorobenzene is not hydrolysed under these conditions, so it gives no precipitate. Ranking by bond polarity instead of bond strength gives chloroethane first.
6. Which reagents and conditions convert benzene into chlorobenzene?
A
Cl2 with anhydrous AlCl3, room temperature
B
Cl2 in ultraviolet light
C
concentrated HCl(aq), heated under reflux
D
Cl2 in aqueous NaOH, room temperature
Show answer
Answer: A. AlCl3 acts as a halogen carrier, polarising Cl2 to give an electrophile that substitutes into the ring. With UV light benzene tends to undergo radical addition rather than give chlorobenzene.
7. Chloroethane and chlorobenzene are each heated with excess concentrated ammonia in ethanol in a sealed tube. Which of them gives an amine?
A
chloroethane only
B
chlorobenzene only
C
both chloroethane and chlorobenzene
D
neither chloroethane nor chlorobenzene
Show answer
Answer: A. Chloroethane undergoes nucleophilic substitution with NH3 to give ethylamine. Chlorobenzene does not react, because its C–Cl bond is strengthened by overlap with the ring and the π electrons repel the nucleophile.
8. A student brominates benzene using bromine and a few iron filings instead of AlBr3. The reaction still gives bromobenzene. Why?
A
iron is a stronger reducing agent than benzene, so it reduces Br2 to Br−, which attacks the ring
B
iron removes HBr from the mixture, so the equilibrium moves to the right
C
iron provides a surface on which bromine molecules split into free radicals
D
iron reacts with bromine to form FeBr3, which acts as a halogen carrier in the same way as AlBr3
Show answer
Answer: D. 2Fe + 3Br2 → 2FeBr3; FeBr3 is a Lewis acid that polarises Br2 and forms Br+. Br− is a nucleophile and cannot attack the electron-rich ring, and free radicals would not give ring substitution.
9. How does the C–Cl bond in chlorobenzene compare with the C–Cl bond in chloroethane?
A
longer and weaker
B
shorter and stronger
C
shorter and weaker
D
longer and stronger
Show answer
Answer: B. Partial overlap of the chlorine lone pair with the π system gives the bond some double-bond character, which makes it both shorter and stronger than the ordinary single bond in chloroethane.
10. Chloroethane reacts with hot aqueous hydroxide ions but chlorobenzene does not. Which statement explains this?
A
the C–Cl bond in chlorobenzene is longer and more polar than the C–Cl bond in chloroethane
B
the ring carbon bonded to Cl is sp3 hybridised and shielded from attack by hydrogen atoms
C
a Cl lone pair overlaps with the π system, giving the C–Cl bond partial double-bond character
D
hydroxide ions add to the ring of chlorobenzene instead, destroying the delocalised system
Show answer
Answer: C. Delocalisation of a chlorine lone pair into the ring strengthens and shortens the C–Cl bond, so it is much harder to break. The ring carbon is sp2, and the bond is less polar, not more.
24, each with the answer and a short explanation, across 1 topics: Halogen compounds. Every chapter test draws ten of them, so you can take it many times.
Is the A Level Chemistry (A2) chapter 9 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
