JAMB Physics 2018 Paper

Concept:Faraday's law of electrolysis relates the mass of a substance deposited to its electrochemical equivalent, the current, and the time of flow.Explanation:The mass deposited is given by the formula $M = Z \cdot I \cdot t$.From the question, $M = 36.0\,\mathrm{g}$, $Z = 0.0012\,\mathrm{g/C}$, and $t = 5\,\mathrm{min}$.Time must be converted to seconds: $t = 5 \times 60 = 300\,\mathrm{s}$.To find the current $I$, rearrange the formula as $I = \frac{M}{Z \cdot t}$.Substitute the known values: $I = \frac{36.0}{0.0012 \times 300}$.Calculate the denominator first: $0.0012 \times 300 = 0.36$.Now divide: $I = \frac{36.0}{0.36} = 100\,\mathrm{A}$.Thus, a steady current of $100\,\mathrm{A}$ will deposit $36.0\,\mathrm{g}$ of silver in 5 minutes.Answer:The current must be $100\,\mathrm{A}$, so the correct option is B.