MCQs on Molecular Orbital Theory

Molecular Orbital Theory was postulated by R.S. Mulliken and F. Hund. It explains the state of bonded electrons in a molecular orbital, which can be represented as a linear combination of atomic orbitals (LCAO). Molecular orbitals are polycentric, where electrons are influenced by more than one nucleus. Bonding molecular orbital is more stable than antibonding molecular orbital. Stability of a molecule can be represented in terms of bond order. The bond order of 1, 2 and 3 represents single, double and triple bond respectively, whereas zero or negative bond order indicates an unstable molecule.

1. Which among the following has the shortest C-C bond length?

(a) Ethene

(b) Ethane

(c) Benzene

(d) Ethyne

2. The oxygen molecule is paramagnetic. It can be explained by

(a) Resonance

(b) Hybridisation

(c) Valence bond theory

(d) Molecular orbital theory

3. Find the paramagnetic species

(a) CN

(b) NO+

(c) CO

(d) O2

4. Find the diamagnetic species

(a) H2

(b) H2

(c) He2+

(d) H2+

5. Which of the following pairs has the same bond order?

(a) O2+, NO+

(b) N2, O2

(c) O22-, B2

(d) NO, CO

6. Each P of P4O10 is attached to how many oxygen atoms?

(a) 3

(b) 2.5

(c) 2

(d) 4

7. When O2 changes to O2, the electron goes to which of the orbitals?

(a) 𝜋 orbital

(b) 𝜎 orbital

(c) 𝜋* orbital

(d) 𝜎* orbital

8. O-O bond length is minimum in

(a) O2

(b) O2

(c) O2+

(d) O22-

9. Which of the following is not paramagnetic?

(a) CO

(b) N2+

(c) NO

(d) O2

10. Find the molecule having the highest bond order

(a) O2+

(b) O2

(c) O22-

(d) O2

Answer

1. (d)

2. (d)

3. (d)

4. (a)

5. (c)

6. (d)

7. (c)

8. (c)

9. (a)

10. (a)

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