Question

Aqueous copper sulphate solution and aqueous silver nitrate solutions are electrolyzed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be the same or different? Explain your answer.

Answer 1

Understanding Faraday’s second law

According to Faraday’s second law of electrolysis, the amount of different substance liberated (𝑊) when same quantity of electricity is passed through electrolytic solution is directly proportional to their chemical equivalent weight (𝐸).

It is mathematically represented as:
$\frac{W_1}{W_2}=\frac{E_1}{E_2}$

Where $E_{1}and{E}_2$ have different values depending upon number of electrons required, to reduce the metal ion.

Finding equivalent weights for Cu and Ag-

$C{u}^{2+}\left(aq\right)+2e^{-}\to Cu\left(s\right)$
$A{g}^{+}\left(aq\right)+e^{-}\to Ag\left(s\right)$

Equivalent weight of $Cu\left(E_1\right)=\frac{MolarMass}{2}$

Equivalent weight of $Ag\left(E_2\right)=\frac{MolarMass}{1}$

Since equivalent weight of Ag and Cu are different,deposited weight of both will be different, with respect to Faraday's second law.

Therefore, different mass of copper and silver are deposited on electrolysis of $CuS{O}_4$ and $AgN{O}_3$ solution in separate electrolytic cell.