Question

If $965$ coulombs of electricity is passed through a metal cup dipped in silver(I) salt solution, in order to plate it with silver. Then the amount of silver deposited on its surface is
(Given: the molar mass of $Ag=108 \, g \, mol^{- 1}, \, 1 \, F=96500$ coulombs)

• A. $1.08g$
• B. $1.002g$
• C. $108g$
• D. $9.89g$

Answer 1

Answer: (A)

The chemical equation for deposition of silver from the salt solution is
$\left(Ag\right)^{+}\left(\right.aq\left.\right)+e^{-}\overset{}{ \rightarrow }Ag\left(\right.s\left.\right)$
Clearly, for deposition of one mole of silver one-mole electrons are required.

• Charge on one mole of the electron is equal to one Faraday or $96500$ Coulombs.
• The mass of one mole of silver is equal to its molar mass, i.e., $108g$ .

Thus, we can say that
$96500$ coulomb charge can deposit $108g$ of silver.
Therefore, $965$ coulomb will deposit $\frac{108}{96500}\times 965=1.08g$ of silver.