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JEE MainChemistryRedox Reactions

When potassium permanganate reacts with potassium iodide in a faintly alkaline medium, the total change in the oxidation state of iodine per molecule of potassium iodide is ________.

Correct answer

6

Step-by-step solution

In a faintly alkaline or neutral medium, potassium permanganate ( KMnO ₄ ) oxidizes iodide ions ( I ^- ) to iodate ions ( IO ₃^- ). The balanced chemical equation for the oxidation half-reaction is: I ^- + 6 OH ^- IO ₃^- + 3 H ₂ O + 6 e ^- The initial oxidation state of iodine in KI is -1 . Let the oxidation state of iodine in IO ₃^- be z . z + 3(-2) = -1 z = +5 The final oxidation state of iodine is +5 . The total change in the oxidation state of iodine is |+5 - (-1)| = 6 . Answer: 6

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