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JAMB Physics 2024 Paper

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Question : 121

Total: 125

Find the amount of current required to deposit 0.02kg of metal in a given electrolysis for 120 seconds. [electro chemical equivalent of the metal = 1.3 x 10 $^{-7}$ kgC $^{-1}$ ]

7.8 x 10 $^{-4}$ A
7.8 x 10 $^{-2}$ A
1.3 x 10 $^{3}$ A
1.3 x 10 $^{5}$ A

Solution:

Concept:

Electrolysis is described by Faraday's law, where the mass deposited depends on current, time, and electrochemical equivalent.

Explanation:

The mass deposited is given by:

m = ZIt

Here,

m = 0.02\,\text{kg}

and

Z = 1.3 \times 10^{-7}\,\text{kgC}^{-1}

.

Time is

t = 120\,\text{s}

.

Make current

I

the subject of the formula:

I = \frac{m}{Zt}

Substitute the given values:

I = \frac{0.02}{1.3 \times 10^{-7} \times 120}

I = \frac{0.02}{1.56 \times 10^{-5}}

I = 1282.05\,\text{A}

This is approximately

1.3 \times 10^{3}\,\text{A}

.

Answer:

1.3 \times 10^{3}\,\text{A}

Option C.

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