Estimate the minimum potential difference needed to reduce Al2O3 at 500o C. The free energy change for the decomposition reaction: 2/3 Al2O3→4/3 Al + O2 is ∆G= +960 kJ

23 Al2O343 Al + O2    is   G= +960 kJG = -nFE0 960 × 103  = 3×43  × 96500 × E0   ( the Al changes from +3 to 0 oxidation state, so 3 electrons are involvefor 1 Al. Therefore for 4/3 Al we need  43 × 3 =4 electrons)E0 =  960 × 1034 × 96500 = 2.487 V

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