250+ TOP MCQs on Structures of Functional Groups and Answers

Chemistry Multiple Choice Questions on “Structures of Functional Groups”.

1. How many lone pairs of electrons does O atom have in methanol?
a) 0
b) 1
c) 2
d) 4
Answer: c
Clarification: The oxygen atom in methanol is sp³ hybridised. One of the sp³ orbitals overlaps with 1s orbital of hydrogen (of OH group) and one sp³ orbital overlaps with sp³ orbital of C atom. The remaining two sp³ orbitals contain one lone pair of electrons each.

2. What is the value of C-O-H bond angle in phenol?
a) 108°
b) 108.9°
c) 109°
d) 109.8°
Answer: c
Clarification: The bond angle C-O-H in phenols is 109° which is slightly more than the C-O-H bond angle in methanol (108.9°) and slightly less than the tetrahedral bond angle (109.5°).

3. If A and B are the C-O bond lengths in methanol and phenol respectively, what is the relationship between A and B?
a) A>B
b) Ac) A=B
d) A≥B

Answer: a
Clarification: The C-O bond length in methanol is 142pm, whereas the C-O bond length in phenol is 136pm, which is slightly less than that in methanol.

4. Which of the following is not a correct reason for the C-O bond length in phenol to be less than that in methanol?
a) Partial double bond character of C-O bond
b) Conjugation of lone pair of electrons with the aromatic ring
c) sp² hybridised sate of carbon of C-O bond
d) Repulsion between the electron lone pairs of oxygen
Answer: d
Clarification: The two lone pairs of electrons of oxygen are present in OH groups of both phenol and methanol and has an effect on the C-O-H bond angle and not the C-O bond length.

5. If the dipole moment of methanol is 1.71D, predict the dipole moment of phenol.
a) 1.54D
b) 1.71D
c) 1.89D
d) 1.96D
View Answer

Answer: a
Clarification: Phenol has a smaller dipole moment than methanol because the C-O bond in phenols is polar due to the electron withdrawing effect of the aromatic ring.

6. The C-O-C bond angle in ethers is _______
a) lesser than 109.5°
b) 109.5°
c) greater than 109.5°
d) 180°
View Answer

Answer: c
Clarification: Due to the repulsive interaction of the bulky alkyl/aryl groups in ethers, the bond angle is slightly more than the tetrahedral angle, i.e., 109.5°. For example, the C-O-C bond angle in methoxymethane is 111.7°.

7. In methanol, the O-H bond length is smaller than the C-O bond length.
a) True
b) False
Answer: a
Clarification: Since hydrogen atom is smaller than the carbon atom and has only 1s orbital, the O-H bond (96pm) is much smaller than the C-O bond (142pm).

8. If the C-O bond length in methanol is 142pm, what will be the C-O bond length in the given compound?

a) 96pm
b) 121pm
c) 141pm
d) 202 pm
Answer: c
Clarification: The shown compound in methoxymethane which is an ether. The C-O bond length in ethers is almost the same as that in alcohols.