Correct decreasing order of boiling point of given compounds:
$I. \ HCl$
$II. \ H_2O$
$III. \ HF$
$IV. \ NH_3$

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

The correct statement/s about Hydrogen bonding is/are:
$A$. Hydrogen bonding exists when $H$ is covalently bonded to a highly electronegative atom.
$B$. Intermolecular $H$ bonding is present in $o$-nitrophenol.
$C$. Intramolecular $H$ bonding is present in $HF$.
$D$. The magnitude of $H$ bonding depends on the physical state of the compound.
$E$. $H$-bonding has a powerful effect on the structure and properties of compounds.
Choose the correct answer from the options given below:

Which of the following molecules forms a linear polymeric structure due to hydrogen bonding?

The hydrides of the first elements in groups $15-17$, namely $NH_3$, $H_2O$ and $HF$ respectively show abnormally high values for melting and boiling points. This is due to

Orthophosphoric acid $(H_3PO_4)$ exhibits high viscosity due to: