# Intermolecular force

Chemistry Level pending

The above shows two types of intermolecular forces. Dipole-dipole interactions are electrostatic interactions between permanent dipoles in molecules. The van der Waals' force (or van der Waals' interaction), named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, the hydrogen bonds, or the electrostatic interaction of ions with one another or with neutral molecules or charged molecules. Van der Waals' forces are relatively weak compared to dipole-dipole forces. Which of the following can be explained by this relative weakness of the Van der Waals' forces?

a) The boiling point of H$$_2$$S is higher than that of O$$_2$$.

b) The boiling point of H$$_2$$O is higher than that of HF.

c) The boiling point of NH$$_3$$ is higher than that of PH$$_3$$.

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