Engineering Chemistry MCQ (Carbocations)

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Engineering Chemistry MCQ (Carbocations)

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1. Stability of free radicals can be explained on the basis of __________
a) Inductive effect
b) Electromeric effect
c) Hyperconjugation
d) Mesomeric effect
Answer: c
Explanation: Stability of free radicals can be explained on the basis of
hyperconjugation effect and ease of formation.

2. The hybridisation of carbocation is __________
a) Sp
b) Sp2
c) Sp3
d) Sp3d
Answer: b
Explanation: The hybridisation of carbocation is sp2. A carbocation is molecule in which a carbon atom bears three bonds and a positive charge.

3. Arrange the following carbocations in the order of increasing stability.
a) Benzyl > 30 > 20 > 10
b) Benzyl > 10 > 20 > 30
c) 30 > 20 > 10 > Benzyl
d) 10 > 20 > 30 > Benzyl
Answer: a
Explanation: The correct stability order of carbocation is- Benzyl > 30 > 20 > 10. Benzyl
carbocation is the most stable and 10 carbocation is least stable.

4. The shape of carbocation is __________
a) Pyramidal
b) Bent
c) Linear
d) Trigonal planar
Answer: d
Explanation: The shape of the carbocation is a trigonal planar. It is sp2 hybridised. A
carbocation is molecule in which a carbon atom bears three bonds and a positive charge.

5. Carbonium ions are the intermediates in which the positive charge is carried by the carbon atom with ___________ electrons in the valence shell.
a) 6
b) 5
c) 4
d) 3
Answer: a
Explanation: Carbonium ions are the intermediates in which the positive charge is
carried by the carbon atom with six electrons in the valence shell. It is an organic
cation in which the positive charge is located on a carbon atom.

6. Positive charge of carbocations can be dispersed by __________
a) (+I) effect of alkyl group
b) Resonance in allyl or benzyl carbocation
c) Hyperconjugation in 10, 20 and 30 carbocations
d) All of the mentioned
Answer: d
Explanation: Positive charge of carbocations can be dispersed by (+I) effect of alkyl
group or by resonance in allyl or benzyl carbocation or by hyperconjugation in 10, 20 and 30 carbocations.

7. Alkyl substitution at the carbon bearing positive charge stabilizes carbocations.
a) True
b) False
Answer: a
Explanation: Alkyl substitution at the carbon bearing positive charge stabilizes
carbocations. Carbocation is a molecule in which a carbon atom bears three bonds and a positive charge.

8. The formal charge at the carbocation is equal to __________
a) -1
b) 0
c) +1
d) +2
Answer: c
Explanation: The formal charge at the carbocation is equal to +1. A carbocation is
molecule in which a carbon atom bears three bonds and a positive charge.

9. The homolytic bond dissociation energy is inversely proportional to the __________
a) Bond length
b) Ease of formation
c) Dipole moment
d) All of the mentioned
Answer: b
Explanation: The homolytic bond dissociation energy is inversely proportional to the
ease of formation of free radicals. Free radicals do not carry any charge.

10. Which of the following free radical has the maximum ease of formation?
a) 10
b) 20
c) 30
d) CH3
Answer: c
Explanation: 30
free radical has the maximum ease of formation. Free radicals do
not carry any charge.