Question:
Given below are two statements:
Statement - I: London forces between two particles are proportional to \(r^{-6}\), where 'r' is the distance between two particles.
Statement - II: The dipole-dipole interaction energy in a solid is proportional to \(r^{-3}\) where r is the distance between two polar molecules.
Given below are two statements:
Statement - I: London forces between two particles are proportional to \(r^{-6}\), where 'r' is the distance between two particles.
Statement - II: The dipole-dipole interaction energy in a solid is proportional to \(r^{-3}\) where r is the distance between two polar molecules.
Statement - I: London forces between two particles are proportional to \(r^{-6}\), where 'r' is the distance between two particles.
Statement - II: The dipole-dipole interaction energy in a solid is proportional to \(r^{-3}\) where r is the distance between two polar molecules.
Show Hint
Always distinguish between fixed-orientation interaction energy (\(r^{-3}\)) and thermally averaged or condensed-phase interaction energy (\(r^{-6}\)) for dipoles.
Updated On: Jun 9, 2026
- Both statement I and statement II are correct
- Both statement I and statement II are not correct
- Statement I is correct, but statement II is not correct
- Statement I is not correct, but statement II is correct
Show Solution
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The Correct Option is C
Solution and Explanation
Concept:
The potential energy of interaction between particles depends on the nature of their dipoles and the state of matter, which influences the range and orientation of the interacting forces. London dispersion forces arise from instantaneous dipole-induced dipole interactions, while dipole-dipole interactions occur between permanent dipoles.
Step 1: Analyze Statement I regarding London forces.
London dispersion forces are the weakest intermolecular forces and arise from the temporary fluctuation in electron density, creating an instantaneous dipole. The potential energy (\(V\)) of interaction for these forces is known to follow an inverse sixth-power law with respect to the distance (\(r\)) between the particles: \[ V \propto \frac{1}{r^6} \] Thus, Statement I is correct.
Step 2: Analyze Statement II regarding dipole-dipole interaction in solids.
The interaction energy between two stationary dipoles with fixed orientation is proportional to \(r^{-3}\). However, in actual solids, molecules are arranged in a lattice where the orientation is often dictated by the crystal structure rather than free dipole-dipole interaction, and the potential energy of interaction for these dipoles generally follows an inverse sixth-power law (\(V \propto r^{-6}\)) when considering the average interactions in a condensed phase. Therefore, Statement II is considered incorrect in the context of standard physical chemistry definitions for solids. \[ \boxed{\text{Statement I is correct, but statement II is not correct}} \]
Step 1: Analyze Statement I regarding London forces.
London dispersion forces are the weakest intermolecular forces and arise from the temporary fluctuation in electron density, creating an instantaneous dipole. The potential energy (\(V\)) of interaction for these forces is known to follow an inverse sixth-power law with respect to the distance (\(r\)) between the particles: \[ V \propto \frac{1}{r^6} \] Thus, Statement I is correct.
Step 2: Analyze Statement II regarding dipole-dipole interaction in solids.
The interaction energy between two stationary dipoles with fixed orientation is proportional to \(r^{-3}\). However, in actual solids, molecules are arranged in a lattice where the orientation is often dictated by the crystal structure rather than free dipole-dipole interaction, and the potential energy of interaction for these dipoles generally follows an inverse sixth-power law (\(V \propto r^{-6}\)) when considering the average interactions in a condensed phase. Therefore, Statement II is considered incorrect in the context of standard physical chemistry definitions for solids. \[ \boxed{\text{Statement I is correct, but statement II is not correct}} \]
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