Question

What are the sulfur oxidation states in sulfuric acid and sulfurous acid?

Answer 1

For `H_2SO_4` we gots `S(VI)`.

Explanation:

For `H_2S_2O_3` we gots `S_"average"(II)`. As always the sum of the oxidation is equal to the charge on the ion/molecule, here neutral.

For `H_2S_2O_3` I like to think that ONE of the oxygens in `H_2SO_4` has been REPLACED by a sulfur atom, and thus assumes the SAME oxidation state (they are both Group VI elements). And so, by this formalism, we gots `S(-II)` and `S(+VI)`.

Of course the average oxidation state is ......

`(S(-II)+S(+VI))/2=+II`,

.........but sometimes the individual assignment of oxidation numbers in poly-sulfur compounds is useful.