Q.1. The bond order and the magnetic characteristic of CN− are (2020)
(1) , diamagnetic
(2) 3, diamagnetic
(3) 3, paramagnetic
(4) , paramagnetic
The molecular electronic configuration of CN– is:
Since, there is no unpaired electron, thus, CN– is diamagnetic in nature.
Q.2. According to molecular orbital theory, which of the following is true with respect to Li2+ and Li2-? (2019)
(1) Li2+ is unstable and Li2- is stable
(2) Li2+ is stable and Li2- is unstable
(3) Both are stable
(4) Both are unstable
Electronic configuratios of Li2+ and Li2-:
Here, both Li2+ and Li2- have positive bond order, thus both are stable.
Q.3. In which of the following processes, the bond order has increased and paramagnetic character has changed to diamagnetic? (2019)
(1) NO → NO+
(2) N2 → N2+
(3) O2 → O2+
(4) O2 → O22-
In case of NO (paramagnetic) → NO+ (diamagnetic) the bond order has increased from 2.5 to 3.
For other cases:
B.O = 2 B.O = 1
Q.4. Two pi and half sigma bonds are present in: (2019)
Q.5. Among the following molecules/ions,Which one is diamagnetic and has the shortest bond length? (2019)
and diamagnetic species has no unpaired electron in their molecular orbitals.
Q.6. Among the following, the molecule expected to be stabilized by anion formation is: (2019)
C2, O2, NO, F2
In case of only C2, incoming electron will enter in the bonding molecular orbital which increases the bond order and stability too. Whereas rest of all takes electron in their antibonding molecular orbital which decreases bond order and stability.
Q.7. Among the following species, the diamagnetic molecule is: (2019)
The molecules with no unpaired electrons are diamagnetic.
Since CO has no unpaired electron. Hence, CO is diamagnetic.
Q.8. During the change of O2 to O2- the incoming electron goes to the orbital: (2019)
Electronic configuration of O2 is
Q.9. The correct statement among the following is : (2019)
(1) (SiH3)3N is planar and less basic than (CH3)5N.
(2) (SiH3)3N is pyramidal and more basic than (CH3)3N.
(3) (SiH3)3N is pyramidal and less basic than (CH3)3N.
(4) (SiH3)3N is planar and more basic than (CH3)3N.
Due to backbonding of lone pair electrons of nitrogen into vacant d-orbitals of Si, trisilylamine (SiH3)3N is planar. In trimethylamine (CH3)3N, there is no backbonding and hence it is more basic.
Q.10. According to molecular orbital theory, which of the following will not be a viable molecule? (2018)
Q.11. In graphite and diamond, the percentage of p-characters of the hybrid orbitals in hybridisation are respectively: (2018)
(1) 67 and 75
(2) 33 and 25
(3) 50 and 75
(4) 33 and 75
= 67 %
Q.12. Which of the following is a Lewis acid? (2018)
Q.13. In the molecular orbital diagram for the molecular ion, N2+, the number of electrons in the σ2p molecular orbital is: (2018)
Q.14. Which of the following conversions involves change in both shape and hybridisation? (2018)
(1) H2O → H3O+
(2) BF3 → BF4–
(3) CH4 →C2H6
(4) NH3 → NH4+
Q.15. The most polar compound among the following is: (2018)
the bond dipole vector of C–F bond is not subtractive.
Q.16. The incorrect geometry is represented by: (2018)
(1) NF3 – trigonal planar
(2) BF3 – trigonal planar
(3) AsF5 – trigonal bipyramidal
(4) H2O – bent
Q.17. Which of the following species is not paramagnetic? (2017)
CO has 14 electrons (even) ∴ It is diamagnetic
NO has 15e-(odd) ∴ It is paramagnetic and has 1 unpaired electron in π*2p molecular orbital.
B2 has 10e- (even) but still paramagnetic and has two unpaired electrons in π2px and π2py (s-p mixing).
O2 has 16 e- (even) but still paramagnetic and has two unpaired electrons in π*2px and π*2py molecular
Q.18. Which of the following is paramagnetic? (2017)
No of e– in
CO = 14, NO+ = 14
= 18, B2 = 10
According to MOT
B2 is paramagnetic
Q.19. sp3d2 hybridization is not displayed by: (2017)
SF6 = Sp3d2 BrF5 = SP3d2
PF5 = sp3d
Q.20. The group having triangular planar structure is (2017)
(1) BF3, NF3, CO32–
(2) CO32–, NO3–, SO3
(3) NH3, SO3, CO32–
(4) NCl3, BCl3, SO3
CO32–, NO3–, SO3 : SP2 Hybridised
Q.21. The species in which the N atom is in a state of sp hybridization is: (2016)
The lewis structure of NO2 shows a bent molecular geometry with trigonal planar electron pair geometry hence the hybridization will be sp2
Q.22. Which one of the following statements about water is FALSE? (2016)
(1) Water is oxidized to oxygen during photosynthesis.
(2) Water can act both as an acid and as a base.
(3) There is extensive intramolecular hydrogen bonding in the condensed phase.
(4) Ice formed by heavy water sinks in normal water.
Water possess intermolecular hydrogen bonding in the condensed phase.