Which of the following orders regarding the melting points of hydrides of group $15$ is correct?

$A$ $p$-block element $(E)$ and hydrogen form a binary cation $(EH_{x}^{+})$, while $EH_{3}$ on treatment with $K_{2}HgI_{4}$ in alkaline medium gives a precipitate of basic mercury$(II)$amido-iodine. Given below are first ionisation enthalpy values $(kJ \ mol^{-1})$ for the first element of each group $13, 14, 15$, and $16$. Identify the correct first ionisation enthalpy value for element $E$.

Nitrogen is obtained when $NaNO_2$ reacts with

Which of the following gases is diamagnetic and neutral towards water?

The metal which displaces hydrogen from a boiling caustic soda solution is

The bond energies (in $kJ \ mol^{-1}$) of $N-H$,$P-H$,and $As-H$ are respectively: