Electrochemistry Result Question 45
45. The standard reduction potential of the $\mathrm{Ag}^{+} / \mathrm{Ag}$ electrode at 298 K is 0.799 V . Given that for $\mathrm{AgI}, K_{\text {sp }}=8.7 \times 10^{-17}$, evaluate the potential of the $\mathrm{Ag}^{+} / \mathrm{Ag}$ electrode in a saturated solution of AgI. Also calculate the standard reduction potential of the $I^- / \mathrm{AgI} / \mathrm{Ag}$ electrode.
(1994, 3M)
Show Answer
Solution:
- In a saturated AgI solution;
$ \begin{alignedat} {\left[\mathrm{Ag}^{+}\right] } & =\sqrt{8.7 \times 10^{-17}} \mathrm{M} \\ & =9.32 \times 10^{-9} \mathrm{M} \\ \Rightarrow \quad E_{\mathrm{Ag}^{+} / \mathrm{Ag}} & =E^{\circ}-0.0592 \log \frac{1}{\left[\mathrm{Ag}^{+}\right]} \\ & =0.799-0.0592 \log \frac{1}{9.32 \times 10^{-9}} \\ & =0.324 \mathrm{~V} \end{aligned} $
Also, for $\quad \mathrm{AgI} \rightleftharpoons \mathrm{Ag}^{+}+\mathrm{I}^{-} ; \quad E^{\circ}= \frac{0.0592}{n} \log K_{\text {sp }} = – 0.95 V$
BETA
