Final answer:
Greater charge enhances intermolecular interactions, like dipole-dipole forces, leading to a lower vapor pressure and higher boiling point. Increased molecular polarizability and surface area also contribute to stronger dispersion forces, affecting the boiling point.
Step-by-step explanation:
The reason greater charge leads to a higher boiling point is that increased charge causes stronger intermolecular forces. Specifically, molecules with permanent dipole moments experience stronger dipole-dipole interactions, which are more substantial than dispersion forces. The types of intermolecular forces, in descending order of strength, are ionic bonding, hydrogen bonding, dipole-dipole interactions, and dispersion forces. The stronger these forces, the lower the vapor pressure of the liquid, and therefore, the higher the boiling point.
For instance, the polar molecule CH2Cl2 has a higher boiling point compared to a nonpolar molecule like CF4 because the polar molecule exhibits dipole-dipole interaction. Also, molecules with higher polarizability, often due to increased molecular size, exhibit larger dispersion forces, contributing to higher boiling points as well.
More generally, any factor that increases the strength of intermolecular interactions between particles—such as increased charge, molecular mass, or surface area—will tend to increase the boiling point of the substance. This relationship is a key principle that helps us to understand the varying boiling points across different substances.