1. Which of the following molecule is least stable?
a) NO+
b) N2
c) NO
d) O2
Explanation: In NO molecule there is a significant difference of about 250 kJ/mol in the energy of atomic orbitals involved.
2. 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*
Explanation: HF molecule has 10 electrons and its electronic configuration is 1s2 2s2 σspx2 [2py2 2pz2] σspx*.
3. 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
Explanation: HF is diamagnetic in nature and O2 is homonuclear molecule. So, only NO is a heteronuclear diatomic molecule that is paramagnetic in nature.
4. 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
Explanation: Cyclohexadiene molecule has two double bonds(hence two π-bonds) and one ring.
5. 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
Explanation: The combination of H (1s1) and F (2px1) gives both bonding (σspx) and antibonding (σspx*) orbitals.
6. 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
Explanation: Valence bond theory does not explain the ionization or gain of electrons, giving O2+ and O2– ions, if O2 has the stable octet.
7. 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
Explanation: He2+ = 0.5, H2, Li2, B2, HF, HCl = 1, NO = 2.5, CO = 3.
8. 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
Explanation: The interaction between pair of orbitals of the same type is repulsive like between σ2s and σ2p orbitals.
9. What are Stereoisomers?
a) Isomers having a same molecular formula and same configuration
b) Isomers having a same molecular formula but different configuration
c) Isomers having a different molecular formula but the same configuration
d) Isomers having a different molecular formula and different configuration
Explanation: Stereoisomerism is exhibited by isomers having the same molecular formula but different configuration.
10. What are diastereomers?
a) Molecules with non-superimposable mirror images
b) Molecules with superimposable mirror images
c) Molecules which do not have non-superimposable mirror images
d) None of the mentioned
Explanation: Diastereomers are those stereomers which do not have non-superimposable mirror images.