Balance the redox equation MnO4− + Fe2+ in acidic solution using the half-reaction method.

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Multiple Choice

Balance the redox equation MnO4− + Fe2+ in acidic solution using the half-reaction method.

Explanation:
Balancing redox in acidic solution requires matching the electron transfer between the oxidizing and reducing couples while using H+ and H2O to balance atoms and charge. Here, permanganate (MnO4−) is reduced to Mn2+ in acidic medium, so the manganese half-reaction must involve a gain of 5 electrons (MnO4− + 8 H+ + 5 e− → Mn2+ + 4 H2O). The iron couple Fe2+ is oxidized to Fe3+ and releases one electron per atom, so its half-reaction is Fe2+ → Fe3+ + e−. To balance electrons, multiply the iron oxidation half-reaction by 5, giving 5 Fe2+ → 5 Fe3+ + 5 e−. Adding the two half-reactions cancels the electrons and yields the balanced overall equation: MnO4− + 8 H+ + 5 Fe2+ → Mn2+ + 4 H2O + 5 Fe3+. The other proposed sets fail because they either use the wrong number of electrons for the MnO4− reduction (it needs 5, not 2), predict a different manganese product (like MnO2) that doesn’t arise in this acidic, MnO4−/Fe2+ system, or do not properly balance both mass and charge after combining the half-reactions.

Balancing redox in acidic solution requires matching the electron transfer between the oxidizing and reducing couples while using H+ and H2O to balance atoms and charge. Here, permanganate (MnO4−) is reduced to Mn2+ in acidic medium, so the manganese half-reaction must involve a gain of 5 electrons (MnO4− + 8 H+ + 5 e− → Mn2+ + 4 H2O). The iron couple Fe2+ is oxidized to Fe3+ and releases one electron per atom, so its half-reaction is Fe2+ → Fe3+ + e−. To balance electrons, multiply the iron oxidation half-reaction by 5, giving 5 Fe2+ → 5 Fe3+ + 5 e−. Adding the two half-reactions cancels the electrons and yields the balanced overall equation: MnO4− + 8 H+ + 5 Fe2+ → Mn2+ + 4 H2O + 5 Fe3+.

The other proposed sets fail because they either use the wrong number of electrons for the MnO4− reduction (it needs 5, not 2), predict a different manganese product (like MnO2) that doesn’t arise in this acidic, MnO4−/Fe2+ system, or do not properly balance both mass and charge after combining the half-reactions.

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