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Using the data E°(MnO4⁻ / Mn²+) = 1.51 V and E°(MnO2 / Mn²+) = 1.23 V, determine the standard electrode potential E° for the couple MnO4⁻ / MnO2.
- 1.70 volt
- 1.51 volt
- 1.23 volt
- 1.00 volt
Correct answer: 1.70 volt
Solution
The MnO4⁻/MnO2 couple is a 3-electron change obtained by subtracting the 2-electron MnO2/Mn2+ reduction from the 5-electron MnO4⁻/Mn2+ reduction. Because potentials cannot be added directly, the free-energy combination gives E° = (5*1.51 - 2*1.23)/3 = 1.70 V.
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