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When aluminium oxide is electrolysed at about 1000°C to obtain aluminium metal, and the cathode process is Al3+ + 3e− → Al, how much electric charge is needed to produce 5.12 kg of aluminium? (Atomic mass of Al = 27 amu; 1 Faraday = 96,500 C)

1. 5.49 × 10¹ C of electricity
2. 5.49 × 10⁴ C of electricity
3. 1.83 × 10⁷ C of electricity
4. 5.49 × 10⁷ C of electricity

Correct answer: 5.49 × 10⁷ C of electricity

Solution

To produce aluminium, the electrolysis process requires a specific amount of electric charge based on the number of moles of Al produced. Given that 5.12 kg of aluminium corresponds to approximately 190 moles, and since each mole of Al requires 3 moles of electrons (3 Faradays), the total charge needed is calculated to be 5.49 × 10⁷ C, making this the correct option.

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