Question

What is the oxidation number of sulfur in dithionous acid?

(a) -3

(b) +3

(c) +6

(d) -6

The question was posed to me in a national level competition.

The doubt is from P-Block Elements in section P-Block Elements of Chemistry – Class 12

Answer 1

Right option is (b) +3

To explain: Dithionous acid is formulated as H2S2O4. Since H can acquire ON of +1 and O of -2 each, then assuming ON of S to be X,

(2 x +1) + (2 x X) + (4 x -2) = 0

On solving, X = +3

The oxidation state/number of sulfur in dithionous acid is +3.