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JAMB Chemistry 1994 Question 28

Question 28

Redox Reactions

MnO4−(aq) + 8H+(aq) + 5Fe2+(aq) → Mn2+(aq) + 5Fe3+(aq) + 4H2O(l). The oxidation number of manganese in the above reaction changed from

  1. A.+7 to +2
  2. B.+6 to +2
  3. C.+5 to +2
  4. D.+4 to +2
Show the answer and explanation

Answer: A (+7 to +2)

Explanation

In MnO4−: Mn + 4(−2) = −1, so Mn = +7. It ends as Mn2+, so the change is +7 to +2.