This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Homonuclear and Heteronuclear Molecules”.
1. Which of the following molecule is not homonuclear?
a) H2
b) N2
c) NO
d) O2
View Answer
Explanation: 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
View Answer
Explanation: Bond order = (10-4)/2 = 3.
3. Which of the following molecule is least stable?
a) NO+
b) N2
c) NO
d) O2
View Answer
Explanation: 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 σspx2 [2py2 2pz2] σspx*
b) 1s2 2s2 σspx2 [2px2 2py2] σspx*
c) 1s2 2s2 σspx2 [2px2 2pz2] σspx*
d) 1s2 2s2 σspx2 [2px4] σspx*
View Answer
Explanation: HF molecule has 10 electrons and its electronic configuration is 1s2 2s2 σspx2 [2py2 2pz2] σspx*.
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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: The combination of H (1s1) and F (2px1) gives both bonding (σspx) and antibonding (σspx*) 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: The interaction between pair of orbitals of the same type is repulsive like between σ2s and σ2p orbitals.
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