The boiling point of hydrogen halides varies in the order:

Contrary to other hydrogen halides,hydrogen fluoride is a liquid because

$PH_3$ has a lower boiling point than $NH_3$. Why?

Among $H_2O, H_2S, H_2Se$ and $H_2Te$,the substance with the highest boiling point is,

Explain the types of Hydrogen bond,provide examples,and discuss their effect on physical properties.

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 $(CH_2OHCH(OH)CH_2OH)$