Which of the following oxyacids contains both $P-H$ and $P-P$ bonds simultaneously?

$NH_3$ can not be obtained by

$A$ $p$-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 $E$.

During the borax bead test with $CuSO_4$,a blue-green colour of the bead was observed in the oxidising flame due to the formation of:

Give the disproportionation reaction of $H_3PO_3$.

When ammonium dichromate is heated,the gas formed is