What is the change in the oxidation state of nitrogen when $HNO_3$ is converted into $N_2O$?

The oxidation number of $N$ in ${N_2}H_5^+$ is:

What is the oxidation state of chlorine atom in hypochlorous acid?

$3 \ mole$ of $N_2H_4$ loses $30 \ mole$ of electrons to form a new compound. Calculate the oxidation state of $N$ in the new compound,assuming the oxidation state of $H$ remains unchanged.

What is the oxidation number of $S$ in $SO_3^{2-}$?

The sum of the oxidation numbers of all the carbons in $C_6H_5CHO$ is