Electrochemistry Result Question 23
23. The standard reduction potentials of $\mathrm{Cu}^{2+} / \mathrm{Cu}$ and $\mathrm{Cu}^{2+} / \mathrm{Cu}^{+}$ are $0.337 \mathrm{~V}$ and $0.153 \mathrm{~V}$ respectively. The standard electrode potential of $\mathrm{Cu}^{+} / \mathrm{Cu}$ half-cell is
$(1997,1 M)$
(a) $0.184 \mathrm{~V}$
(b) $0.827 \mathrm{~V}$
(c) $0.521 \mathrm{~V}$
(d) $0.490 \mathrm{~V}$
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Answer:
Correct Answer: 23. ( c )
Solution:
- $E^{\circ}$ is an intensive property :
$E^{\circ} \quad \Delta G^{\circ}=-n E^{\circ} F$
(i) $\mathrm{Cu}^{2+}+2 e^{-} \longrightarrow \mathrm{Cu} \quad 0.337 \mathrm{~V} \quad-0.674 \mathrm{~F}$
(ii) $\mathrm{Cu}^{2+}+e^{-} \longrightarrow \mathrm{Cu}^{+} \quad 0.153 \mathrm{~V} \quad-0.153 \mathrm{~F}$
Subtracting (ii) from (i) gives :
$ \begin{aligned} & \mathrm{Cu}^{+}+e^{-} \longrightarrow \mathrm{Cu} \\ & \Delta G^{\circ}=-0.521 \mathrm{~F}=-n E^{\circ} \mathrm{F} \\ \Rightarrow & \quad E^{\circ}=0.521 \mathrm{~V} \\ \because & \quad n=1 \end{aligned} $
BETA
