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Electrochemistry — Chemistry STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry3 Marks
Question
Aqueous copper sulphate solution and aqueous silver nitrate solution are electrolysed by $1$ ampere current for $10$ minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different? Explain your answer.
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Answer

It will be different. According to Faraday’s second law, the amounts of different substances liberated by the same quantity of electricity passing through the electrolytic solution are proportional to their chemical equivalent weights, $\frac{\text{Atomic mass of metal}}{\text{No. of electrons}}$ electrons required to reduce the cation. Here, for the electrode reactions:
$\text{Cu}^{2+}+2\text{e}^{-}\xrightarrow{\ \ \ \ \ \ \ \ \ \ \ \ }\text{Cu(s)}$
$\text{Ag}^{+}+\text{e}^{-}\xrightarrow{\ \ \ \ \ \ \ \ \ \ \ \ }\text{Ag(s)}$
Hence, one mole of $Cu^{2+} $ and $Ag^{3+}$ require $2 \ mol$ of electron $(2F)$ and $1 \ mol$ of electrons $(F1)$ respectively.

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