The correct statements (s) about intermolecular forces is(are)
- A
The potential energy between two point charges approaches zero more rapidly than the potential energy between a point dipole and a point charge as the distance between them approaches infinity.
- B
The average potential energy of two rotating polar molecules that are separated by a distance has dependence.
- C
The dipole-induced dipole average interaction energy is independent of temperature.
- D
Nonpolar molecules attract one another even though neither has a permanent dipole moment.
Recall the distance-dependence of the major interaction energies:
(A) Ion-ion potential energy , ion-dipole potential energy . The ion-ion term falls off slower with , not faster, so (A) is incorrect.
(B) For two freely rotating polar molecules (Keesom interaction), the Boltzmann-averaged potential energy scales as , not . (B) is incorrect.
(C) The Debye interaction (dipole-induced dipole) depends on permanent dipole moment and polarisability but is essentially temperature-independent because the induced dipole follows the inducing field instantaneously. (C) is correct.
(D) Nonpolar molecules still attract through London dispersion forces, which arise from instantaneous correlated fluctuations of electron clouds. (D) is correct.
Correct options are (C) and (D).
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