The Gibbs energy for the decomposition of Al2O3 at 500oC is as follows: 23Al2O3→43Al+O2;ΔrG=+96kJ The voltage needed for the electrolytic reduction of aluminium oxide (Al2O3) at 500oC is at least:
A
−4.5V
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B
−3.0V
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C
−2.5V
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D
−5.0V
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Solution
The correct option is A−2.5V ΔG=−nFEon=4
For decomposition of Al2O3, 4 moles of electrons are transferred.