Electrochemistry 2 Question 48
47. The standard reduction potential of $\mathrm{Cu}^{2+} / \mathrm{Cu}$ and $\mathrm{Ag}^{+} / \mathrm{Ag}$ electrodes are 0.337 and $0.799 \mathrm{~V}$ respectively. Construct a galvanic cell using these electrodes so that its standard emf is positive. For what concentration of $\mathrm{Ag}^{+}$will the emf of the cell, at $25^{\circ} \mathrm{C}$, be zero if the concentration of $\mathrm{Cu}^{2+}$ is $0.01 \mathrm{M}$ ?
(1990, 3M)
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Solution:
- The galvanic cell is : $\mathrm{Cu}\left|\mathrm{Cu}^{2+} | \mathrm{Ag}^{+}\right| \mathrm{Ag}$ Cell reaction : $\mathrm{Cu}+2 \mathrm{Ag}^{+} \rightleftharpoons \mathrm{Cu}^{2+}+2 \mathrm{Ag}, E^{\circ}=0.462 \mathrm{~V}$
$$ E=0=0.462-\frac{0.0592}{2} \log \frac{(0.01)}{\left[\mathrm{Ag}^{+}\right]^{2}} $$
$$ \Rightarrow \quad\left[\mathrm{Ag}^{+}\right]=1.57 \times 10^{-9} \mathrm{M} $$
