Question

What distinguishes `HF`, `H_2O`, and `CH_4` in terms of intermolecular force?

Answer 1

Water has the lowest vapour pressure, the highest viscosity, and the lowest vapour pressure.

Explanation:

These characters can be attributed to the degree of intermolecular forces that operate in each substance. Methane, a room temperature gas, with relatively non-polar `C-H` bonds, has the least degree of intermolecular interaction, even thout the individual `C-H` bonds are strong.

Hydrogen fluoride and water can both support extensive hydrogen bonding due to the polarization of the `H-X` bond and the alignment of dipoles between molecules. This intermolecular force accounts for the elevated boiling points of `HF` (`19.5` `""^@C`) and water, in comparison to the lower Group analogues.