The number of hydrogen bonds formed by a water molecule at normal conditions is

In which of the following is intramolecular $H$-bonding absent?

Maximum number of hydrogen bonds in $H_2O$ is

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 $(CH_2OHCH(OH)CH_2OH)$

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

Define hydrogen bond. Is it weaker or stronger than the van der Waals forces?