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MHT CET202618 April 2026Morning ShiftChemistryRedox ReactionsActual

What happens in the oxidation number of Mn during working of dry cell.

Options

  1. AIncreases by 1
  2. Bdecreases by 1
  3. CIncreases by 2
  4. Ddecreases by 2

Correct answer

B. decreases by 1

Step-by-step solution

In a dry cell, the reaction at the cathode involves the reduction of manganese dioxide ( MnO₂ ). The cathode reaction is: MnO₂ + NH₄^+ + e^- MnO(OH) + NH₃ The oxidation state of Mn in MnO₂ is +4 . The oxidation state of Mn in MnO(OH) is +3 . The oxidation number of Mn changes from +4 to +3 . Thus, the oxidation number of Mn decreases by 1 . Answer: decreases by 1

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