Cyanogen gas is obtained in the reaction:

Which one of the following is not correct?

Explain the molecular structure and properties of phosphorus trichloride $(PCl_{3})$.

When a brown compound of manganese $(A)$ is treated with $HCl$,it gives a gas $(B)$. The gas $(B)$ taken in excess reacts with $NH_3$ to give an explosive compound $(C)$. The compounds $A$,$B$ and $C$ are:

$N_2O_3$ is a/an.......