The oxidation number of $S$ in $H_2S_2O_8$ is

What is the oxidation state of $S$ in the sulphur-containing product of the following reaction?
$SO_3^{2-}{_{\text{(aq)}}} + Br_{2\text{(l)}} + H_2O_{\text{(l)}} \rightarrow $

In which of the following molecules or ions does sulphur have the minimum oxidation number?

Sulphur has the lowest oxidation number in

Oxidation number of nitrogen in $NaNO_2$ is

Select the compound in which chlorine is assigned the oxidation number $+5$.