JAMB Chemistry 2014 Paper

Concept:The quantity of electricity needed is found from the moles of electrons required to reduce copper ions.Explanation:Copper is liberated from a copper(II) compound by the reaction:$\mathrm{Cu^{2+} + 2e^- \rightarrow Cu}$This shows that $1$ mole of copper needs $2$ moles of electrons.The charge carried by $1$ mole of electrons is Faraday's constant, $F = 96500\,\mathrm{C\,mol^{-1}}$.The molar mass of copper is $64\,\mathrm{g\,mol^{-1}}$.Therefore, $64\,\mathrm{g}$ of copper requires $2 \times 96500\,\mathrm{C}$ of electricity.For $10\,\mathrm{g}$ of copper, the charge $Q$ is calculated by proportion:$Q = \frac{10}{64} \times 2 \times 96500$$Q = \frac{10 \times 2 \times 96500}{64}$$Q = 30156.25\,\mathrm{C}$So the quantity of electricity required is approximately $30156.3\,\mathrm{C}$.Answer:$30156.3\,\mathrm{C}$ (Option B).