Which nitrogen trihalide is the least basic?

Give the disproportionation reaction of $H_3PO_3$.

Sodium nitrite is reacted with $H_2SO_4$ to form $NaHSO_4$,$HNO_3$,water and $X$. Gold is dissolved in aqua regia to form water,$AuCl_4^{-}$ and $Y$. $X$ and $Y$ are respectively

The structure of white phosphorus is ........ .

Enlist the main uses of nitrogen.

Consider the following statements:-
$I. \, PCl_3$ hydrolyses in the presence of moisture giving fumes of $HCl$.
$II. \, PCl_5$ exists as $[PCl_4]^+[PCl_6]^-$ in the solid state.
$III. \, $All the five bonds in the $PCl_5$ molecule are equivalent.
Choose the correct statements.