250+ TOP MCQs on Homonuclear and Heteronuclear Molecules and Answers

Engineering Chemistry Multiple Choice Questions on “Homonuclear and Heteronuclear Molecules”.

1. Which of the following molecule is not homonuclear?
a) H₂
b) N₂
c) NO
d) O₂
Answer: c
Clarification: NO is Heteronuclear diatomic molecule in which atomic number of nitrogen is 7 and that of oxygen is 8 i.e., total number of electrons = 15.

2. Bond order of NO⁺ molecule is _________
a) 2
b) 3
c) 2.5
d) 4
Answer: b
Clarification: Bond order = (10-4)/2 = 3.

3. Which of the following molecule is least stable?
a) NO⁺
b) N₂
c) NO
d) O₂
Answer: c
Clarification: In NO molecule there is a significant difference of about 250 kJ/mol in the energy of atomic orbitals involved.

4. The molecular orbital electronic configuration of HF molecule is _________
a) 1s² 2s² σ_spx² [2_py² 2_pz²] σ_spx*
b) 1s² 2s² σ_spx² [2_px² 2_py²] σ_spx*
c) 1s² 2s² σ_spx² [2_px² 2_pz²] σ_spx*
d) 1s² 2s² σ_spx² [2_px⁴] σ_spx*
Answer: a
Clarification: HF molecule has 10 electrons and its electronic configuration is 1s² 2s² σ_spx² [2_py² 2_pz²] σ_spx*.

5. From the following options, choose the heteronuclear diatomic molecules which are paramagnetic in nature?
a) HF and NO
b) HF and O₂
c) NO and O₂
d) Only NO
Answer: d
Clarification: HF is diamagnetic in nature and O₂ is homonuclear molecule. So, only NO is a heteronuclear diatomic molecule that is paramagnetic in nature.

6. Calculate the number of σ and π bonds in cyclohexadiene. (C₆H₈)
a) σ bond = 2, π bond = 14
b) σ bond = 14, π bond = 2
c) σ bond = 12, π bond = 2
d) σ bond = 12, π bond = 4
Answer: b
Clarification: Cyclohexadiene molecule has two double bonds(hence two π-bonds) and one ring.

7. The combination of H (1s¹) and F (2px¹) gives _________
a) Bonding orbital
b) Antibonding orbital
c) Both bonding and antibonding orbital
d) None of the mentioned
Answer: c
Clarification: The combination of H (1s1) and F (2px1) gives both bonding (σ_spx) and antibonding (σ_spx*) orbitals.

8. Choose the incorrect option from the following.
a) Valence bond theory does not explain the paramagnetic nature of O₂
b) Molecular orbital theory explains the extra stability of O₂⁺ cation over O₂
c) Valence bond theory explains the ionization or gain of electrons, giving O₂⁺ and O₂^– ions, if O₂ has the stable octet
d) Resonance has no role in Molecular orbital theory
Answer: c
Clarification: Valence bond theory does not explain the ionization or gain of electrons, giving O₂⁺ and O₂^– ions, if O₂ has the stable octet.

9. Which of the following molecules have bond order equal to 1?
a) NO, HF, HCl, Li₂, CO
b) H₂, Li₂, B₂, HF, HCl
c) Li₂, B₂, CO, NO,He₂⁺
d) B₂, CO, He₂⁺, NO, HF
Answer: b
Clarification: He₂⁺ = 0.5, H₂, Li₂, B₂, HF, HCl = 1, NO = 2.5, CO = 3.

10. The interaction between a pair of orbitals of the same type is _________
a) Attractive
b) Repulsive
c) There is no interaction
d) None of the mentioned
Answer: b
Clarification: The interaction between pair of orbitals of the same type is repulsive like between σ_2s and σ_2p orbitals.