In neutral solution, thiosulphate is oxidized by potassium permanganate to

\(SO_4^{2-}\)

The correct answer is option 3. \(SO_4^{2-}\).

In the reaction between thiosulfate (\(S_2O_3^{2-}\)) and potassium permanganate (\(KMnO_4\)) in a neutral solution, the following reaction occurs:

\(\text{S}_2\text{O}_3^{2-} + 4 \text{MnO}_4^- + 6 \text{H}^+ \rightarrow 2 \text{SO}_4^{2-} + 4 \text{Mn}^{2+} + 3 \text{H}_2\text{O}\)

In this reaction, each thiosulfate ion (\(S_2O_3^{2-}\)) is oxidized to sulfate (\(SO_4^{2-}\)). The sulfur atoms in thiosulfate undergo oxidation from a lower oxidation state of +2 in thiosulfate to a higher oxidation state of +6 in sulfate.

Potassium permanganate acts as an oxidizing agent in this reaction, while thiosulfate is being oxidized. The permanganate ion (\(MnO_4^-\)) gets reduced to manganese ions (\(Mn^{2+}\)) during the process.

Overall, the reaction results in the formation of sulfate ions (\(SO_4^{2-}\)), making option 3 the correct choice.