20 multiple-choice questions with five alternatives each (A–E) about Cyclic Hydrocarbons in Organic Chemistry. The answers with extended explanations are presented at the end.
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Multiple-Choice Questions: Cyclic Hydrocarbons
1. What are cyclic hydrocarbons?
A) Compounds with branched chains
B) Compounds containing oxygen atoms
C) Compounds where carbon atoms form a closed ring
D) Compounds with triple bonds only
E) Compounds with sulfur atoms
2. Which of the following is a cyclic hydrocarbon?
A) Propane
B) Ethane
C) Cyclopropane
D) Butyne
E) Benzaldehyde
3. What is the general formula for cycloalkanes?
A) CₙH₂ₙ
B) CₙH₂ₙ₊₂
C) CₙHₙ
D) CₙH₂ₙ₋₂
E) CₙH₂ₙ₊₄
4. Which of these is the smallest possible cycloalkane?
A) Cyclopentane
B) Cyclopropane
C) Cyclobutane
D) Cyclohexane
E) Cyclooctane
5. What is the IUPAC name for a six-carbon cyclic alkane?
A) Hexane
B) Cyclohexene
C) Cyclohexane
D) Benzene
E) Hexyne
6. Which statement is TRUE about cyclopropane?
A) It is linear
B) It has a stable ring structure
C) It has a three-carbon ring
D) It contains a double bond
E) It is aromatic
7. What type of hybridization do carbon atoms have in cycloalkanes?
A) sp
B) sp²
C) sp³
D) dsp³
E) sp³d
8. Which of the following compounds is aromatic?
A) Cyclopentane
B) Cyclohexane
C) Cyclopropane
D) Benzene
E) Cyclobutene
9. What is a distinguishing property of aromatic cyclic hydrocarbons?
A) High reactivity like alkenes
B) Presence of triple bonds
C) Alternating double and single bonds in a stable ring
D) Presence of branched alkyl chains
E) Being ionic in nature
10. How many carbon atoms are in cyclopentane?
A) 3
B) 4
C) 5
D) 6
E) 7
11. What is the molecular formula of cyclobutane?
A) C₄H₈
B) C₄H₁₀
C) C₄H₆
D) C₄H₄
E) C₄H₉
12. Which of the following is NOT a cycloalkane?
A) Cyclohexane
B) Cyclopentane
C) Cyclopropane
D) Benzene
E) Cyclobutane
13. What causes angle strain in small cycloalkanes like cyclopropane?
A) Excess hydrogen atoms
B) Lone pairs on carbon
C) Bond angles deviating from tetrahedral geometry
D) Presence of oxygen
E) Aromaticity
14. Which of the following cycloalkanes has the least angle strain?
A) Cyclopropane
B) Cyclobutane
C) Cyclopentane
D) Cyclohexane
E) Cycloheptane
15. What is a common reaction of cycloalkanes?
A) Elimination
B) Addition
C) Nucleophilic substitution
D) Combustion
E) Hydrogenation
16. What is the name of a compound with a benzene ring and a methyl group attached?
A) Toluene
B) Phenol
C) Aniline
D) Benzaldehyde
E) Styrene
17. What type of isomerism is possible in substituted cycloalkanes?
A) Optical only
B) Structural only
C) Chain only
D) Geometrical (cis-trans)
E) Functional only
18. Which of the following compounds has a six-carbon ring with alternating double bonds?
A) Cyclohexane
B) Cyclohexene
C) Benzene
D) Cyclopentene
E) Phenol
19. What is the hybridization of each carbon atom in benzene?
A) sp
B) sp²
C) sp³
D) dsp³
E) sp²d
20. Which of the following is true about the stability of benzene?
A) It is less stable than alkenes
B) It is unstable due to resonance
C) It is stabilized by delocalized π electrons
D) It reacts easily with bromine
E) It is linear in structure
- Questions about Branched Alkanes in Organic Chemistry
- Questions about Alkenes and Alkynes (Organic Chemistry)
- Questions about Structural Isomers and Stereoisomers (Organic Chemistry)
✅ Answer Key with Extended Explanations
1. C – Cyclic hydrocarbons have carbon atoms forming a ring structure.
2. C – Cyclopropane is a three-carbon cyclic alkane.
3. A – Cycloalkanes follow the formula CₙH₂ₙ, due to the ring formation.
4. B – Cyclopropane is the smallest cycloalkane with only three carbon atoms.
5. C – Cyclohexane is a six-carbon ring with only single bonds.
6. C – Cyclopropane is a triangle-shaped molecule with three carbon atoms.
7. C – Carbon atoms in cycloalkanes are sp³ hybridized, like in alkanes.
8. D – Benzene is aromatic, with delocalized electrons in a six-membered ring.
9. C – Aromatic compounds have alternating single and double bonds in a ring.
10. C – Cyclopentane contains five carbon atoms.
11. A – Cyclobutane (C₄H₈) follows the cycloalkane formula CₙH₂ₙ.
12. D – Benzene is not a cycloalkane; it’s an aromatic hydrocarbon.
13. C – Small rings like cyclopropane suffer angle strain from tight bond angles.
14. D – Cyclohexane has bond angles close to 109.5°, minimizing angle strain.
15. D – Like other hydrocarbons, cycloalkanes undergo combustion reactions.
16. A – Benzene with a methyl group is known as toluene.
17. D – Substituted cycloalkanes can show cis-trans isomerism due to ring rigidity.
18. C – Benzene has six carbon atoms and alternating double bonds in a ring.
19. B – Carbon atoms in benzene are sp² hybridized, allowing delocalized π bonding.
20. C – Benzene is very stable due to resonance and delocalized π electrons.
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