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JAMB Chemistry 2024 Paper

Question : 19

Total: 138

Solution:

Concept:

Silver ions (

\mathrm{Ag}^{+}

) are reduced to silver atoms by gaining one electron each.

One mole of silver requires one faraday of electricity.

Explanation:

The cathode half-reaction is:

\mathrm{Ag}^{+} + e^{-} \rightarrow \mathrm{Ag}

This shows that

1

mole of

\mathrm{Ag}

is deposited by

1

faraday, since one electron is needed per silver atom.

Molar mass of silver,

\mathrm{Ag}

, is

108\ \mathrm{g\,mol^{-1}}

Thus,

108\ \mathrm{g}

of silver requires

1\ \mathrm{F}

The given mass is

180\ \mathrm{g}

of silver.

Set up the proportion:

\frac{x}{180} = \frac{1}{108}

So,

x = \frac{180}{108} = 1.666...\ \mathrm{F}

Rounded to two decimal places,

x = 1.67\ \mathrm{F}

Therefore, the quantity of electricity needed is

1.67

faradays.

Answer:

1.67\ \mathrm{F}

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