Question

The molecular weight of $H_{2}S$ is more than that of $H_{2}O$, but $H_{2}S$ is a gas and $H_{2}O$ is a liquid. Explain.

Answer 1

The molecular weight of H${}_2$S is more than that of H${}_2$O, but H${}_2$S is a gas and H${}_2$O is a liquid. In H${}_2$O molecules, due to formation of intermolecular hydrogen bonds, there is molecular association. Large amount of energy is required to break these intermolecular hydrogen bonds. Hence, the boiling point of H${}_2$O is very high and it is a liquid. Intermolecular hydrogen bonding is not possible in H${}_2$S. Hence, its boiling point is lower and is a gas.