How many moles of electrons are needed to deposit 0.4 mol of aluminium from Al³⁺?

A) 0.4 mol e⁻

B) 2.4 mol e⁻

C) 1.2 mol e⁻

D) 2.2 mol e⁻

Answer: C

Explanation: Each Al³⁺ ion requires 3 electron(s) to form one metal atom. 0.4 mol metal therefore needs 0.4 × 3 = 1.2 mol electrons.