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JAMB Chemistry 2018 Paper

Question : 51

Total: 87

^{2+}

_{4}

^{-1}

, Cu=64)

Solution:

Concept:

Electrolysis relates the mass of substance liberated at an electrode to the current, time, molar mass, and number of electrons involved.

Explanation:

For the cathodic reduction of

\mathrm{Cu}^{2+}

, the mass of copper deposited is given by the formula:

m = \frac{M I t}{z F}

where

M = 64\ \mathrm{g\,mol^{-1}}

I = 1.60\ \mathrm{A}

t = 1\ \mathrm{hour} = 3600\ \mathrm{s}

z = 2

, and

F = 96500\ \mathrm{C\,mol^{-1}}

Substitute the values into the formula:

m = \frac{64 \times 1.60 \times 3600}{96500 \times 2}

m = \frac{368640}{193000} = 1.91\ \mathrm{g}

Answer:

The mass of copper produced is 1.91 g, which is Option C.

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