$Ortho$-nitrophenol is steam volatile whereas $para$-nitrophenol is not. This is due to

Acetic acid exists as a dimer in benzene due to:

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 $(CH_2OHCH(OH)CH_2OH)$

Which of the following statements is incorrect?

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

The boiling point of water is higher than that of liquid $HF$. The reason is that