Question

In neutral or faintly alkaline medium, KMnO4 being a powerful oxidant can oxidize, thiosulphate almost quantitatively, to sulphate. In this reaction overall change in oxidation state of manganese will be

• A. 5
• B. 1
• C. 0
• D. 3

Answer 1

Answer: (D)

3

Answer 2

Under neutral or slightly alkaline conditions, thiosulfate undergoes nearly complete oxidation to form sulfate ions, as indicated by the following reaction:
$8MnO_{4}^−+3S_2O_{3}^{2−}+H_2O→8MnO_2+6SO_{4}^{2−}+2OH^−$
Here the Mn changes from Mn+7 to Mn+4
Thus, overall change in its oxidation number would be of 3.
So, the correct option is (D): 3