Which of the following metals produces nitrous oxide $(N_2O)$ when reacted with dilute $HNO_3$?

Which of the following halides does not exist?

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

In the ring test of $NO_{3}^{-}$ ion,$Fe^{2+}$ ion reduces nitrate ion to nitric oxide,which combines with $Fe^{2+}_{(aq)}$ ion to form a brown complex. Write the reactions involved in the formation of the brown ring.

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:

Which of the following statements is correct regarding $H_3PO_3$ and $H_3PO_4$?