Which of the following substances does not produce ammonia upon heating?

White phosphorus,when heated with conc. $NaOH$ solution in an inert atmosphere of $CO_2$,forms phosphine and a sodium salt of oxoacid of phosphorus,$'X'$. The oxidation state of phosphorus in $'X'$ is

Which of the following pairs of oxoacids have a basicity of $2$?

Which allotropic form of phosphorus is the most stable,least reactive,and possesses a graphite-like structure?

When $KNO_3$ is heated with concentrated $H_2SO_4$,brown fumes are evolved. These fumes are due to:

$A$ colourless,neutral,paramagnetic oxide of nitrogen '$P$' on oxidation gives reddish brown gas $Q$. $Q$ on cooling gives colourless gas $R$. $R$ on reaction with $P$ gives blue solid $S$. Identify $P, Q, R, S$ respectively.