Engineering Chemistry MCQ (Mesomeric Effect)

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Engineering Chemistry MCQ (Mesomeric Effect)

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1. In mesomeric effect, the electrons are transferred from __________
a) A multiple bonds to an atom
b) A multiple bonds to a single covalent bond
c) An atom with a lone pair to the adjacent single covalent bond
d) All of the mentioned
Answer: d
Explanation: In the mesomeric effect, the electrons are transferred from multiple
bonds to an atom, a multiple bond to a single covalent bond and an atom with the
lone pair to the adjacent single covalent bond.

2. Which of the following is a resonance effect?
a) Inductive effect
b) Electromeric effect
c) Mesomeric effect
d) Inductomeric effect
Answer: c
Explanation: Mesomeric effect is also known as the resonance effect. The
mesomeric effect is a permanent effect and operates in compounds containing at least one double bond.

3. The phenomenon in which 2 or more structures, involving identical position of atoms can be written for a particular molecule, is called __________
a) Conjugation
b) Resonance
c) Hyper conjugation
d) Vibration
Answer: b
Explanation: The phenomenon in which 2 or more structures, involving the identical
position of atoms can be written for a particular molecule, is called resonance. The
mesomeric effect is a permanent effect and operates in compounds containing at least one double bond.

4. Select the incorrect option from the following option.
a) Resonating structures have a real existence
b) The actual structure lies between various possible resonating structures
c) Resonating structures are useful as they allow us to describe molecules
d) None of the mentioned
Answer: a
Explanation: Resonating structures have no real existence. All the other options are
correct. The actual structure lies between various possible resonating structures,
resonating structures are useful as they allow us to describe molecules.

5. The resonance energy is defined as a difference in energy between __________
a) Two consecutive resonating structures
b) Resonance hybrid and most unstable resonating structure
c) Resonance hybrid and most stable resonating structure
d) First and last resonating structures
Answer: c
Explanation: The resonance energy is defined as a difference in energy between
resonance hybrid and most stable resonating structure. The resonance energy of a
compound is a measure of the extra stability of the conjugated system compared to the corresponding number of isolated double bonds.

6. Which of the following is an application of the mesomeric effect?
a) Dipole moment
b) Strength of acids and bases
c) Bond length
d) All of the mentioned
Answer: d
Explanation: Dipole moment, strength of acids and bases and bond length are some of the applications of the mesomeric effect.

7. Dipole moment of CH3-CH2-Cl > CH2=CH-Cl.
a) True
b) False
Answer: a
Explanation: Dipole moment of CH3-CH2-Cl > CH2=CH-Cl. This is due to resonance in vinyl chloride.

8. Select the correct statement from the following option.
a) Benzene ring has two different types of bond length for single and double bonds
b) All the bond length in benzene ring is equal due to hyperconjugation
c) All the bond length in benzene ring is equal due to resonance
d) All of the mentioned
Answer: c
Explanation: All the bond length in the benzene ring is equal due to resonance. All
the bond lengths are equal in benzene ring i.e. double bond as well as single bond due to resonance.

9. Greater the number of resonating structures for a given intermediate __________
a) Less will be its stability
b) More will be its stability
c) It will not affect its stability
d) None of the mentioned
Answer: b
Explanation: Greater the number of resonating structures for a given intermediate,
more will be its stability. More resonating structure increases stability.

10. Phenyl group show __________
a) (+M) effect
b) (+E) effect
c) (+I) effect
d) (-M) effect
Answer: d
Explanation: Phenyl group show (-M) effect. The phenyl group or phenyl ring is a
cyclic group of atoms with the formula C6H5.