Question

Find the oxidation number of S in $H_2{S}_2{O}_8$.

Answer 1

Let X be the oxidation number of S in $H_2{S}_2{O}_8$.
One peroxo linkage is present which is $O-O$ linkage. The O atoms of this linkage have oxidation number of -1. The remaining O atoms have oxidation number of -2.
The oxidation number of H is +1.
$2(+1)+2X+2(-1)+6(-2)=0$
$2X-12=0$
$2X=12$
$X=+6$
The oxidation number of S in $H_2{S}_2{O}_8$ is $+6$.