Which of the following dissolves in hot conc. $NaOH$ solution?

Identify the reactions in which $N_2$ is liberated.
$a. \ (NH_4)_2SO_4 + NaOH \longrightarrow$
$b. \ NH_3 + Cl_2 \longrightarrow$ (excess $Cl_2$ is not specified, but $N_2$ is formed when $NH_3$ is in excess)
$c. \ (NH_4)_2Cr_2O_7 \xrightarrow{\Delta}$
$d. \ NH_4NO_3 \xrightarrow{\Delta}$
$e. \ NH_4Cl_{(aq)} + NaNO_{2_{(aq)}} \longrightarrow$

Define the order of $d_{P-O}$ (single bond length) in the given compounds $X$ and $Y$:
$P_4 \xrightarrow{O_2} 'X'$
$P_4 \xrightarrow{O_2 \text{ (excess)}} 'Y'$

The strongest base is

Which of the following is not correct?

The correct decreasing order of basicity of hydrides of group-$15$ elements is