question_answer

Sulphur dioxide is a more powerful reducing agent in the alkaline medium than in the acidic medium. Assign reason.

Answer:

                The reducing nature of \[S{{O}_{2}}\] in the alkaline medium is shown by the following equation. \[S{{O}_{2}}+2O{{H}^{-}}\,S{{O}_{4}}^{2-}\,+2{{H}^{+}}\,+2{{e}^{-}}\] The addition of acid \[({{H}^{+}})\]favours the reverse reaction. Therefore, sulphur dioxide fails to act as reducing agent in the acidic medium. In the alkaline medium, \[{{H}^{+}}\] ions formed as the products are removed. This favours the forward reaction. As a result, \[S{{O}_{2}}\]acts as a reducing agent in the alkaline medium.