Chapter Exam

Chapter 9: Hydrocarbons — Online MCQ Test

Q: Which of the following is an alkane?

Answer: C. Ethane — Ethane is a saturated hydrocarbon containing only single bonds. Ethene and ethyne are unsaturated, while benzene is aromatic.

Q: The general formula of alkenes is:

Answer: B. C_nH_2n — Alkenes are open-chain hydrocarbons with one double bond, and their general formula is C_nH_2n.

Q: An alkene is converted into an alkane by which type of reaction?

Answer: B. Addition of hydrogen — Hydrogen adds across the double bond in hydrogenation, converting an alkene to an alkane.

Q: A hydrocarbon has molecular formula C4H8. Which inference is most correct?

Answer: B. It can be an alkene or cycloalkane — C4H8 fits the general formula C_nH_2n, which is shared by alkenes and cycloalkanes. Formula alone cannot distinguish them.

CHEMISTRY · CLASS 11 FIRST PUC · Karnataka State Board

Practice Chapter 9: Hydrocarbons with a free chapter-wise online MCQ test for Karnataka State Board CLASS 11 FIRST PUC CHEMISTRY. This chapter covers: Alkanes Alkenes Alkynes Aromatic hydrocarbons Benzene Saturated Unsaturated Addition reaction Substitution reaction Combustion Cracking. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 9: Hydrocarbons — Important Questions & Answers (FAQ)

Frequently asked questions from Karnataka State Board CLASS 11 FIRST PUC CHEMISTRY — Chapter 9: Hydrocarbons, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is an alkane?

A. Ethene
B. Ethyne
C. Ethane ✓
D. Benzene

Answer: C. Ethane
Ethane is a saturated hydrocarbon containing only single bonds. Ethene and ethyne are unsaturated, while benzene is aromatic.

The general formula of alkenes is:

A. C_nH_2n+2
B. C_nH_2n ✓
C. C_nH_2n-2
D. C_nH_n

Answer: B. C_nH_2n
Alkenes are open-chain hydrocarbons with one double bond, and their general formula is C_nH_2n.

An alkene is converted into an alkane by which type of reaction?

A. Substitution
B. Addition of hydrogen ✓
C. Elimination
D. Combustion

Answer: B. Addition of hydrogen
Hydrogen adds across the double bond in hydrogenation, converting an alkene to an alkane.

A hydrocarbon does not decolourise bromine water at room temperature. Which conclusion is most appropriate?

A. It must be an alkene
B. It must be an alkyne
C. It may be an alkane or benzene under ordinary conditions ✓
D. It must contain oxygen

Answer: C. It may be an alkane or benzene under ordinary conditions
Alkanes do not react with bromine water without UV light, and benzene also does not readily decolourise bromine water without a catalyst.

A hydrocarbon has molecular formula C4H8. Which inference is most correct?

A. It must be an alkane
B. It can be an alkene or cycloalkane ✓
C. It must be an alkyne
D. It must be benzene

Answer: B. It can be an alkene or cycloalkane
C4H8 fits the general formula C_nH_2n, which is shared by alkenes and cycloalkanes. Formula alone cannot distinguish them.

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