What is the change in oxidation number of $Cr$ in the following redox reaction?
$3H_2O_2(aq) + Cr_2O_7^{2-}(aq) + 8H^+(aq) \rightarrow 3O_2(g) + 2Cr^{3+}(aq) + 7H_2O(l)$

State whether the following statements are True or False:
$(1)$ The oxidation number of nitrogen in ammonium chloride $(NH_4Cl)$ is $(-3)$.
$(2)$ The oxidation number of $C$ in methyl chloride $(CH_3Cl)$ is $(-2)$.
$(3)$ In the following reaction,the oxidation number of $Br$ changes from $0$ to $+5$: $Br_2 \to BrO_3^-$.

The oxidation state of nitrogen is highest in

Calculate the correct increasing order of average oxidation number of sulphur in $S_8, S_2O_3^{2-}, S_2O_7^{2-}, S_4O_6^{2-}, SO_3^{2-}$

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

The oxidation states of $S$ atoms in Caro's acid and Marshall's acid are