In neutral or faintly alkaline medium, $$KMnO_4$$ being a powerful oxidant can oxidise, thiosulphate almost quantitatively, to sulphate. In this reaction overall change in oxidation state of manganese will be

We are told that in neutral or faintly alkaline medium, $$KMnO_4$$ oxidises thiosulphate to sulphate. We need to find the overall change in oxidation state of manganese.

In $$KMnO_4$$, the oxidation state of Mn is $$+7$$. Now, in a neutral or faintly alkaline medium, $$KMnO_4$$ is reduced to $$MnO_2$$ (manganese dioxide), where Mn has an oxidation state of $$+4$$.

We can verify this: in strongly acidic medium, $$MnO_4^-$$ is reduced to $$Mn^{2+}$$ (change of 5). In strongly alkaline medium, it is reduced to $$MnO_4^{2-}$$ (change of 1). But in neutral or faintly alkaline medium, the product is $$MnO_2$$.

The change in oxidation state of manganese is:

$$\Delta = +7 - (+4) = 3$$

Hence, the overall change in oxidation state of manganese is 3.

Hence, the correct answer is Option D: 3.