Oxidation number of $S$ in $Na_2SO_4$ is

The oxidation number and covalency of sulphur in the sulphur molecule $S_8$ are respectively

What is the change in oxidation number of carbon in the following reaction?
$CH_{4(g)} + 4Cl_{2(g)} \rightarrow CCl_{4(l)} + 4HCl_{(g)}$

What is the oxidation state of $S$ in $H_2SO_3$?

The characteristic oxidation number of atoms in free metals is

$3 \ mole$ 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.