WAEC Chemistry 2022 Paper

Concept:Electrolysis of molten or aqueous $\mathrm{AlCl}_3$ requires the reduction of $\mathrm{Al}^{3+}$ ions at the cathode.Explanation:$\mathrm{AlCl}_3$ ionises as:$\mathrm{AlCl}_3 \rightarrow \mathrm{Al}^{3+} + 3\mathrm{Cl}^-$At the cathode, aluminium ions gain electrons:$\mathrm{Al}^{3+} + 3e^- \rightarrow \mathrm{Al}$One mole of $\mathrm{Al}^{3+}$ ions needs $3$ moles of electrons to form one mole of aluminium atoms.One mole of electrons carries a charge of $1$ Faraday ($1\,F$).Therefore, $3$ moles of electrons carry $3\,F$ of charge.So, the electricity required is $3$ Faradays.Answer:C. Three Faradays