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WAEC Chemistry 2010 Objective — Question 37

Question 37 of 49 from the West African Examinations Council (WAEC) Chemistry 2010 Objective paper, with the correct answer and a full explanation.

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What is the change in oxidation number of manganese in the reaction represented by the following equation? MnO4⁻(aq)+8H⁺(aq)+5e⁻→Mn²⁺(aq)+4H2O(l)

  • A. A. +7 to +2Correct
  • B. B. +4 to +2
  • C. C. +6 to +2
  • D. D. +7 to +4

Explanation

The oxidation number of manganese in MnO4⁻ is +7 while its value in Mn²⁺ is +2. Thus, manganese has undergone a change of oxidation number from +7 to +2.

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