When chlorine reacts with a gas $X,$ an explosive inorganic compound $Y$ is formed. Then $X$ and $Y$ will be

Phosphorus can be stored in

$A$ 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.

The oxoacid of phosphorus which contains $4 \ P-O-H$ bonds, $2 \ P=O$ bonds, and one $P-O-P$ bond is

Ammonia on reaction with hypochlorite anion,can form

Aqua regia is used for dissolving noble metals ($Au$,$Pt$,etc.). The gas evolved in this process is: