What happens when an acidic solution of the green compound (B) is allowed to stand for some time ? Also write the equation involved. What is this type of reaction called ?
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Solution and Explanation
Step 1: Behaviour in acidic medium When an acidic solution of potassium manganate is allowed to stand, the green colour gradually disappears and a purple solution of potassium permanganate is formed along with manganese dioxide. This occurs because manganese in oxidation state (+6) undergoes both oxidation and reduction simultaneously.
Step 2: Chemical equation [ 3MnO_4^2- +4H^+ 2MnO_4^- +MnO_2 +2H_2O ]
Step 3: Nature of the reaction In the above reaction:
• One portion of manganese is oxidized from (+6) to (+7).
• Another portion is reduced from (+6) to (+4).
Since the same species undergoes oxidation as well as reduction simultaneously, the reaction is called a disproportionation reaction.
Final Answer [ 3MnO_4^2-+4H^+ 2MnO_4^-+MnO_2+2H_2O ] [ This reaction is called a disproportionation reaction. ]
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