How many moles of KMnO4 are required to completely oxidize 5 moles of Ferrous ion (Fe2+) in acidic medium? (Hard)
Answer and explanation
Correct answer: B. 1 mole
- Step 1: The balanced ionic half-reactions: MnO4- + 8 H+ + 5 e- -> Mn2+ + 4 H2O and 5 Fe2+ -> 5 Fe3+ + 5 e-. Step 2. The stoichiometry is 1 mole of MnO4- per 5 moles of Fe2+. Thus exactly 1 mole of KMnO4 is required. Answer: 1 mole. Why not the others: 5 moles assumes 1:1 stoichiometry; 2 moles is used in dichromate ratios; 3 moles is arithmetic error.
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