Chapter Exam

Chapter-14 Organic Chemistry — Online MCQ Test

Q: What is the general molecular formula for alkanes?

Answer: B. CₙH₂ₙ₊₂ — Alkanes are saturated hydrocarbons with only single bonds between carbon atoms, following the general formula CₙH₂ₙ₊₂.

Q: Which of the following is an alkene?

Answer: B. Ethene (C₂H₄) — Ethene (C₂H₄) contains a carbon-carbon double bond (C=C), which is the characteristic feature of alkenes.

Q: A compound with molecular formula C₅H₁₂ reacts with bromine water but does not decolorize it. What can be concluded?

Answer: B. The compound is an alkane — C₅H₁₂ fits the alkane formula CₙH₂ₙ₊₂. Since it does not decolorize bromine water, it lacks C=C double bonds and must be an alkane (pentane).

Q: Which of the following compounds would produce a white precipitate when added to bromine water followed by addition of ammonia solution?

Answer: B. Phenol — Phenol reacts with bromine water to form a white precipitate of 2,4,6-tribromophenol. This is a characteristic test for phenols, not found in alkenes, alcohols, or alkanes.

CHEMISTRY · Grade 10 · IGCSE cambridge

Practice Chapter-14 Organic Chemistry with a free chapter-wise online MCQ test for IGCSE cambridge Grade 10 CHEMISTRY. This chapter covers: Alkanes alkenes alcohols and carboxylic acids fuels polymers and basic organic reactions.. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-14 Organic Chemistry — Important Questions & Answers (FAQ)

Frequently asked questions from IGCSE cambridge Grade 10 CHEMISTRY — Chapter-14 Organic Chemistry, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the general molecular formula for alkanes?

A. CₙH₂ₙ
B. CₙH₂ₙ₊₂ ✓
C. CₙH₂ₙ₋₂
D. CₙHₙ

Answer: B. CₙH₂ₙ₊₂
Alkanes are saturated hydrocarbons with only single bonds between carbon atoms, following the general formula CₙH₂ₙ₊₂.

Which of the following is an alkene?

A. Ethane (C₂H₆)
B. Ethene (C₂H₄) ✓
C. Ethyne (C₂H₂)
D. Ethanol (C₂H₆O)

Answer: B. Ethene (C₂H₄)
Ethene (C₂H₄) contains a carbon-carbon double bond (C=C), which is the characteristic feature of alkenes.

Why do alkenes decolorize bromine water while alkanes do not?

A. Alkenes are more reactive due to the presence of C=C double bonds ✓
B. Alkanes have stronger bonds than alkenes
C. Alkenes contain more hydrogen atoms
D. Alkanes are insoluble in bromine water

Answer: A. Alkenes are more reactive due to the presence of C=C double bonds
The C=C double bond in alkenes is reactive and undergoes addition reaction with bromine, causing decolorization. Alkanes with only single bonds do not readily react with bromine.

A compound with molecular formula C₅H₁₂ reacts with bromine water but does not decolorize it. What can be concluded?

A. The compound is an alkene
B. The compound is an alkane ✓
C. The compound is an alcohol
D. The compound is a carboxylic acid

Answer: B. The compound is an alkane
C₅H₁₂ fits the alkane formula CₙH₂ₙ₊₂. Since it does not decolorize bromine water, it lacks C=C double bonds and must be an alkane (pentane).

Which of the following compounds would produce a white precipitate when added to bromine water followed by addition of ammonia solution?

A. Ethene
B. Phenol ✓
C. Ethanol
D. Methane

Answer: B. Phenol
Phenol reacts with bromine water to form a white precipitate of 2,4,6-tribromophenol. This is a characteristic test for phenols, not found in alkenes, alcohols, or alkanes.

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