Which of the following reacts with $Fe(II)$ ions to form a brown complex?

The nitrogen-containing compound produced in the reaction of $HNO_3$ with $P_4O_{10}$:
$(A)$ can also be prepared by the reaction of $P_4$ and $HNO_3$
$(B)$ is diamagnetic
$(C)$ contains one $N-N$ bond
$(D)$ reacts with $Na$ metal producing a brown gas

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{P}Cl_5 + H_2O \longrightarrow H_3PO_4 + HCl$

Heating $P_4O_{10}$ with water yields ..............

Which of the following statements is not true for nitrogen?

Which one of the following can be used as an anaesthetic?