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We consider the following redox system: $Fe^{3+}$ // $Fe^{3+}$ $E^o$= $0.75 \;V$ What is his → potential under the standard conditions for $[Fe^{3+}]$ $=$ $0.1 \frac{mol}{L}$ et $[Fe^{2+}]$ $=$ $2\cdot 10^{-3} \frac{mol}{L}$?
$E$ $ =$ $ E^o+\frac{0.059}{n}log\frac{[Fe^{3+}]}{[Fe^{2+}]}$
$n\; =\; 1$ because $Fe^{3+}$ + 1 $e^- $ $\leftrightarrows$ $Fe^{2+}$
$E$ $ =$ $ 0.75+\frac{0.059}{1}log(\frac{0.1}{0.002})$ $ =$ $0.85\;V$