Question

For molecules of comparable mass, why are dipole-dipole forces stronger than dispersion forces?

A) Dipole-dipole forces involve specific areas of the molecule, while dispersion acts throughout.
B) Dipole-dipole exists between permanent dipoles, while London dispersion exists between temporary dipoles.
C) Dipole-dipole forces are intra-molecular and are stronger than intermolecular forces.
D) Dipole-dipole forces occur between molecules, and London dispersion forces do not.

Answer 1

Dipole-dipole forces are stronger than dispersion forces for molecules of similar mass because they arise from permanent dipoles in polar molecules, while dispersion forces are due to temporary dipoles in all molecules.

Step-by-step explanation:

For molecules of comparable mass, dipole-dipole forces are stronger than dispersion forces because dipole-dipole forces exist between permanent dipoles, while dispersion forces (also known as London dispersion forces) occur between temporary dipoles.

Dipole-dipole interactions result from a net unequal distribution of electrons within polar molecules, creating a partial positive charge on one side and a negative charge on the other. This creates an electrostatic attraction that is more consistent and stronger than the transient attractions in dispersion forces, which are due to the instantaneous and random distribution of electrons that create only momentary dipoles.