What is the oxidation number of sulphur in $Na_2S_4O_6$?

What is the oxidation state of $S$ in $SO_4^{2-}$?

When zinc reacts with very dilute $HNO_3$,the oxidation state of nitrogen changes from

$KMnO_4$ acts as an oxidising agent in the neutral medium and gets reduced to $MnO_2$. What is the equivalent weight of $KMnO_4$ in a neutral medium?

Which of the following is $NOT$ correct for $C_3O_2$?

The oxidation number of $Mn$ in $KMnO_4$ is