ΔG° can be calculated from the cell potential using the following equation:
ΔG° = Gibbs Free Energy, J
n = # of e- transferred
F = Faraday’s constant = 96485 J/(mol e-)
E°cell = standard cell potential, V
ΔG°f for Fe2+(aq):
Fe2+(aq) + 2 e- → Fe(s) E° = -0.447 V
n = 2 mol e-
F = 96485 C/(mol e-)
E° = -0.447 V
ΔG°rxn = 86257.59 J
ΔG°rxn = 86.26 kJ
ΔG˚f, Fe2+ = –86.26 kJ/mol Fe2+
ΔG°f for Fe3+(aq):
The equation ΔG° = -nFE° also can be applied to half-reactions. Use standard reduction potentials to estimate ΔG°f for Fe2+(aq) and Fe3+(aq). (ΔG°f for e- = 0.)
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Our tutors have indicated that to solve this problem you will need to apply the Cell Potential concept. If you need more Cell Potential practice, you can also practice Cell Potential practice problems.
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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl 2nd Edition practice problems.