Chemistry - Redox Reactions Question with Solution | TestHub

Let the oxidation state of S be $x$.

The oxidation state of oxygen is generally $-2$.

The sum of oxidation states of all atoms in a polyatomic ion is equal to the net charge on the ion.

For ${\mathrm{SO}}_4^{2-}$:

$x+4(-2)=-2$

$x-8=-2$

$x=+6$

Answer: +6