Statement I: In electrolysis, the quantity of electricity needed for depositing 1 mole of silver is — Electrochemistry Chemistry Question

💡 Solution & Explanation

\textbf{Assertion (I):} The same quantity of electricity deposits different masses of silver and copper. \textbf{Reason (II):} The molar masses of silver and copper are different. \textbf{Analysis:} By Faraday's law of electrolysis: \[ m = \frac{Q \times M}{n_e \times F} = \frac{Q \times E_{\text{eq}}}{F} \] where $E_{\text{eq}} = M/n_e$ is the \textbf{equivalent mass}. For Ag: $M = 108$, $n_e = 1$, so $E_{\text{eq}}(\text{Ag}) = 108\ \text{g/eq}$ For Cu: $M = 63.5$, $n_e = 2$, so $E_{\text{eq}}(\text{Cu}) = 31.75\ \text{g/eq}$ Since the equivalent masses differ, the same charge Q deposits different masses. \textbf{Statement I is correct.} \textbf{Statement II is incorrect} because it attributes the difference to \textit{molar mass} alone — but the actual reason is the difference in \textit{equivalent mass} ($M/n_e$). If Cu were singly charged with the same molar mass, it would deposit much more per coulomb than Ag. \textbf{Answer: B} (Statement I correct, Statement II incorrect)