In which of the following compounds does hydrolysis take place through $S_N^1$ and $S_N^2$ mechanisms respectively?

Which of the following is an amphoteric oxide?

The oxidation number of phosphorus varies from

Given below are two statements:
Statement-$I$: Element '$X$' and '$Y$' are the most and least electronegative elements, respectively, among $N, As, Sb$ and $P$. The nature of the oxides $X_{2}O_{3}$ and $Y_{2}O_{3}$ is acidic and amphoteric, respectively.
Statement-$II$: $BCl_{3}$ is covalent in nature and gets hydrolysed in water. It produces $[B(OH)_{4}]^{-}$ and $HCl$ in aqueous medium.

Which of the following oxides of nitrogen is the anhydride of nitrous acid?

The stable bivalency of $Pb$ and trivalency of $Bi$ is