Which of the following has the strongest $H$-bond?

The correct order of boiling points of hydrogen halides is

Bond energy of covalent $O-H$ bond in water is

Explain why $HCl$ is a gas and $HF$ is a liquid?

Viscosity of a liquid arises due to strong intermolecular forces existing between the molecules. Stronger the intermolecular forces,greater is the viscosity. Name the intermolecular forces existing in the following liquids and arrange them in the increasing order of their viscosities. Also give reason for the assigned order in one line.
Water,hexane $(CH_3CH_2CH_2CH_2CH_2CH_3)$,glycerine $(CH_2OHCH(OH)CH_2OH)$

$NH_3$ has a much higher boiling point than $PH_3$ because