Question

Aluminium oxide may be electrolysed at 1000°C to furnish aluminium metal.

(Atomic mass = 27 amu; 1 Faraday = 96,500 coulombs)

The cathode reaction is:

\[\ce{Al^3+ + 3e- -> Al^0}\]

To prepare 5.12 kg of aluminium metal by this method would require:

Options

• 5.49 × 10¹ C of electricity

• 5.49 × 10⁴ C of electricity

• 1.83 × 10⁷ C of electricity

• 5.49 × 10⁷ C of electricity

Answer 1

5.49 × 10⁷ C of electricity

Explanation:

The reaction \[\ce{Al^3+ + 3e- -> Al}\] shows that 1 g of Al³⁺ requires 3 Faraday (i.e., 3 × 96500 C) of electricity. Hence, electricity is required to prepare 5.12 kg (5120 g) of Al.

= `(3 xx 96500)/27 xx 5120`

= 5.49 × 10⁷ C