Question

Oxidation number of sulphur in marshall's acid $\left(H_2{S}_2{O}_8\right)$ is

• A. $+5$
• B. $+8$
• C. $+6$
• D. $+7$

Answer 1

The correct option is C $+6$

Let $x$ be the oxidation number of sulphur in marshall's acid $\left(H_2{S}_2{O}_8\right)$. It contains a peroxide linkage. Thus, the oxidation number of two O atoms is $-1$ and that of the remaining O atoms is $-2$. The oxidation number of H is $+1$.
For the neutral molecule, the sum of the oxidation numbers is zero.
Therefore, $2(+1)+2x+2(-1)+6(-2)=0$ or, $x=+6$
The structure is given below: