Practise 18 real Federal Board questions on Alkyl Halides from 2023 to 2026. See the answer and explanation as soon as you answer.
Alkyl Halides is one of the 19 main chapters in our Federal Board FSC Chemistry question bank (11th and 12th class), and about 4% of its real questions come from it. Tayyari Karo has 18 real questions on this chapter from 2023 to 2026; 7 are multiple choice and marked instantly, and the rest are short and long questions with a model answer. By difficulty: 13 medium, 4 hard, 1 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.
When chloroethane reacts with aqueous OH⁻ at low temperature, main product is:
Answer: B. Ethanol
Aqueous OH⁻ (a good nucleophile, low temperature favors substitution over elimination) reacts with chloroethane via SN2 to give ethanol.
Nitriles are prepared from halogenoalkanes by reaction with KCN. This is an example of:
Answer: A. Nucleophilic substitution
CN⁻ (nucleophile) displaces the halide leaving group from the alkyl halide via nucleophilic substitution (SN2).
Identify the product formed when Ethyl Bromide is warmed with NaOH in ethanol:
Answer: A. CH₂=CH₂
Alcoholic (ethanolic) NaOH/KOH favours elimination (E2), removing HBr from ethyl bromide to give ethene, CH₂=CH₂.
Which of the following alkyl halides will yield alkenes more easily among the given options?
Answer: B. 2-Methyl-2-Bromo Propane
A tertiary halide like 2-methyl-2-bromopropane forms a stable tertiary carbocation, favouring fast E1 elimination to give an alkene.
Which of the following is a bad leaving group?
Answer: C. F⁻
F⁻ is a poor leaving group due to its small size, high charge density, and the very strong C–F bond.
In SN1 reaction, the rate depends on:
Answer: C. Concentration of substrate
SN1 is a first-order (unimolecular) reaction: rate = k[substrate], depending only on substrate concentration (rate-determining step is carbocation formation).
Classify Halogenoalkanes based on the type of halogen atom and its position in carbon chain.
By type of halogen atom: Fluoroalkanes (R-F), Chloroalkanes (R-Cl), Bromoalkanes (R-Br), Iodoalkanes (R-I).
By position of halogen (degree of substitution of the carbon bearing X):
1. Primary (1°) halogenoalkane: halogen attached to a carbon bonded to only one other carbon, e.g. CH₃CH₂Cl.
2. Secondary (2°) halogenoalkane: halogen attached to a carbon bonded to two other carbons, e.g. (CH₃)₂CHCl.
3. Tertiary (3°) halogenoalkane: halogen attached to a carbon bonded to three other carbons, e.g. (CH₃)₃CCl.
Give three differences between SN1 and SN2 reactions.
SN1SN2Two-step mechanism via a carbocation intermediateOne-step, concerted mechanism (no intermediate)Rate depends only on [substrate] (first order)Rate depends on both [substrate] and [nucleophile] (second order)Favored by tertiary substrates (stable carbocation)Favored by primary substrates (less steric hindrance)
| Session | Questions |
|---|---|
| 2026 Annual | 3 |
| 2025 1st Annual | 8 |
| 2025 2nd Annual | 2 |
| 2024 Annual | 4 |
| 2023 Annual | 1 |
18 real Federal Board (FBISE) Chemistry questions on Alkyl Halides from 2023 to 2026, for 11th and 12th class. Each one shows the session it came from.
No. We could not find an official FBISE marking scheme for these papers, so the answers and explanations are written by Tayyari Karo for practice. Check anything important with your teacher or textbook.
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