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Hydrocarbons ISC Class 11 MCQ & Practice Questions

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Hydrocarbons Revision Guide for ISC Class 11 Chemistry

Hydrocarbons is part of ISC Class 11 Chemistry preparation. A strong revision plan should combine concept review with exam-style questions so that definitions, relationships, calculations and exceptions are recalled accurately.

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Important Topics

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  • Important equations or relationships
  • Common applications and examples
  • Frequently confused concepts
  • Exam-style multiple-choice questions
  • Error review and targeted revision

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What to practise in Hydrocarbons

Concept Revision

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Exam-style MCQs

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Top 20 Hydrocarbons MCQs with Answers

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ISC Class 11 Chemistry · Hydrocarbons · Very Hard

1. The general formula of open-chain alkanes is:

  • A. CnH2n-2
  • B. CnHn
  • C. CnH2n+2
  • D. CnH2n
Answer: C
Explanation: Acyclic saturated hydrocarbons follow CnH2n+2.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

2. The carbon atoms in methane are described as:

  • A. dsp2 hybridised
  • B. sp3 hybridised
  • C. sp2 hybridised
  • D. sp hybridised
Answer: B
Explanation: Methane has four sigma bonds arranged tetrahedrally around sp3 carbon.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

3. The approximate H-C-H bond angle in methane is:

  • A. 109.5°
  • B. 120°
  • C. 180°
  • D. 90°
Answer: A
Explanation: Methane has tetrahedral geometry.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

4. Wurtz reaction is useful for preparing:

  • A. Alkenes from alcohols
  • B. Alkynes from calcium carbide
  • C. Arenes from phenols
  • D. Higher alkanes from alkyl halides
Answer: D
Explanation: Alkyl halides couple with sodium in dry ether to form alkanes.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

5. Decarboxylation of sodium carboxylate with soda lime gives an alkane having:

  • A. Same number of carbons always
  • B. Two carbons more
  • C. One carbon less
  • D. One carbon more
Answer: C
Explanation: Loss of the carboxyl carbon as carbonate gives an alkane with one fewer carbon.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

6. Kolbe electrolysis of sodium acetate mainly produces:

  • A. Ethyne
  • B. Ethane
  • C. Methane
  • D. Ethene
Answer: B
Explanation: Methyl radicals formed at the anode couple to produce ethane.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

7. Halogenation of methane proceeds mainly through:

  • A. Free-radical substitution
  • B. Electrophilic addition
  • C. Nucleophilic substitution
  • D. Elimination
Answer: A
Explanation: Photochemical chlorination proceeds by a radical chain mechanism.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

8. The initiation step in chlorination of methane involves:

  • A. Heterolytic cleavage of C-H
  • B. Formation of carbocation
  • C. Attack by OH-
  • D. Homolytic cleavage of Cl-Cl
Answer: D
Explanation: Light causes Cl2 to split homolytically into chlorine radicals.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

9. Complete combustion of an alkane produces:

  • A. Carbon and H2
  • B. Alcohol only
  • C. CO2 and H2O
  • D. CO and H2 only
Answer: C
Explanation: Sufficient oxygen converts carbon to CO2 and hydrogen to water.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

10. Pyrolysis of higher alkanes generally produces:

  • A. Only carboxylic acids
  • B. Smaller hydrocarbons
  • C. Only CO2
  • D. Only alcohols
Answer: B
Explanation: Thermal cracking breaks larger hydrocarbons into smaller alkanes and alkenes.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

11. The most stable conformation of ethane is:

  • A. Staggered
  • B. Eclipsed
  • C. Planar square
  • D. Cis
Answer: A
Explanation: Staggering minimises torsional strain.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

12. The eclipsed conformation of ethane has:

  • A. Lower energy than staggered
  • B. No C-H bonds
  • C. A carbon-carbon double bond
  • D. Higher torsional strain than staggered
Answer: D
Explanation: Bonding electron pairs eclipse one another, increasing torsional strain.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

13. The general formula of acyclic monoalkenes is:

  • A. CnH2n-2
  • B. CnHn
  • C. CnH2n
  • D. CnH2n+2
Answer: C
Explanation: One C=C reduces hydrogen count by two relative to the corresponding alkane.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

14. Carbon atoms of the C=C bond in ethene are:

  • A. d2sp3 hybridised
  • B. sp2 hybridised
  • C. sp3 hybridised
  • D. sp hybridised
Answer: B
Explanation: Each carbon uses three sp2 orbitals and one unhybridised p orbital.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

15. A carbon-carbon double bond contains:

  • A. One sigma and one pi bond
  • B. Two sigma bonds
  • C. Two pi bonds
  • D. One sigma and two pi bonds
Answer: A
Explanation: The double bond consists of one sigma and one pi bond.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

16. Rotation around a carbon-carbon double bond is restricted mainly because:

  • A. The sigma bond is absent
  • B. Carbon becomes ionic
  • C. Hydrogen bonding occurs
  • D. Rotation would disrupt p-orbital overlap
Answer: D
Explanation: The pi bond requires parallel p orbitals and restricts free rotation.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

17. Geometrical isomerism in alkenes requires each double-bonded carbon to have:

  • A. No substituents
  • B. Only hydrogen atoms
  • C. Two different substituents
  • D. Two identical substituents
Answer: C
Explanation: Different groups on each alkene carbon allow distinct cis/trans or E/Z arrangements.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

18. Dehydration of an alcohol commonly gives:

  • A. An aromatic hydrocarbon only
  • B. An alkene
  • C. An alkane only
  • D. An alkyne directly always
Answer: B
Explanation: Elimination of water from suitable alcohols forms alkenes.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

19. Dehydrohalogenation of an alkyl halide generally produces:

  • A. An alkene
  • B. An alcohol
  • C. An alkane
  • D. A carboxylic acid
Answer: A
Explanation: Removal of HX from adjacent atoms creates a C=C bond.

ISC Class 11 Chemistry · Hydrocarbons · Very Hard

20. Saytzeff's rule predicts preferential formation of:

  • A. The least substituted alkene always
  • B. Only methane
  • C. An alkyne
  • D. The more substituted alkene
Answer: D
Explanation: Beta elimination commonly favours the more substituted, more stable alkene.

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Hydrocarbons Practice Tests

Hydrocarbons Frequently Asked Questions

How should I prepare Hydrocarbons for ISC Class 11 Chemistry?

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