Which gas is used to provide an inert atmosphere?

Explain the nature of oxide compounds of group-$15$ elements.

When $PbO_2$ reacts with concentrated $HNO_3$,the evolved gas is:

$Y$ in the given sequence of reactions is
$P_4 + x NaOH + y H_2O \xrightarrow{CO_2} X + z NaH_2PO_2$
$X + CuSO_4 \rightarrow Y + H_2SO_4$

White phosphorus reacts with thionyl chloride to give

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{N}Cl_3 + 3H_2O \longrightarrow 3HOCl + NH_3$