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The Gibb's energy for the decomposition of Al_(2)O_(3) at 500^(@)C is as follows (2)/(3)Al_(2)O_(3) rarr (4)/(3)Al+O_(2) Delta_(f) = 960 kJ mol^(-1) The potential difference needed for the electrolytic reduction of aluminium oxide (Al_(2)O_(3)) at 500^(@)C us at least |
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Answer» `4.5 V` `{:("At anode: " 2O^(2-)+4e^(-)rarrO_(3)"]" xx 3),("At anode: " Al^(3+) rarr Al + 3e^(-)"]" xx 4),(ul(BAR("Net REACTION:" 4AL^(3+)+6O_(2-) rarr 3O_(2)+4Al))),(or 4//3 Al^(3+) + 2O^(2-) rarr O_(2)+4//3Al):}` `:. n = (12)/(3) = 4` `Delta G^(@) = -NFE^(@)` `960 xx 1000 = -4 xx 96500 xx E^(@)` [Here `Delta G^(@) = +960 kJ mol^(-1) = 960 xx 1000 J mol^(-1), n = 4, F = 96500 "coulomb mol"^(-1)]` or `E^(@) = -2.48 V` Potential difference needed `= 2.5 V` |
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