The reason for the exceptionally high boiling point of water is

The strongest intermolecular hydrogen bond is present in which of the following pairs of molecules?

When ice melts to form liquid water at $0\,^{\circ}C$,there is a contraction in volume. This is due to

Assertion : Boiling point of $p$-nitrophenol is higher than that of $o$-nitrophenol.
Reason : $p$-nitrophenol has intermolecular hydrogen bond whereas $o$-nitrophenol has intramolecular hydrogen bond.

$HCl$ is a gas but $HF$ is a low boiling liquid. This is because

The dominant intermolecular force that must be overcome to convert liquid methanol to its vapour is