Question

The following reaction occurs during rusting of iron

${\text{2H}}^{\text{+}}\text{+}\text{2e}\text{+}\frac{\text{1}}{\text{2}}{\text{O}}_{\text{2}}\to {\text{H}}_{\text{2}}\text{O;}{\text{E}}^{\text{o}}\text{ =}\text{+1}\text{.23}\text{V}$

${\mathrm{Fe}}^{2+}+2\mathrm{e}\to \mathrm{Fe}(\mathrm{s});{\mathrm{E}}^0=0.44\mathrm{V}$

Calculate magnitude of ${\left(\text{ΔG}\right)}^{\text{o}}\text{(kJ)}$ for the net process

$\text{Fe}\text{(s)}\text{+}{\left(\text{2H}\right)}^{\text{+}}\text{+}\frac{\text{1}}{\text{2}}{\left(\text{O}\right)}_{\text{2}}\to {\left(\text{Fe}\right)}^{\text{2+}}\text{+}{\left(\text{H}\right)}_{\text{2}}\text{O}$

Answer 1

Answer: 322

$Fe(s)\to F{e}^{2+}+2e^{-};\Delta G_1^0$

$2H^{+}+2e^{-}+\frac{1}{2}{O}_2\to H_{2}O(1);\Delta G_2^0$

$Fe(s)+2H^{+}+\frac{1}{2}{O}_2\to F{e}^{2+}+H_{2}O;\Delta G_3^0$

Applying, $\Delta G_1^o+\Delta G_2^0=\Delta G_3^0$

$\Delta G_3^o=(-2F\times 0.44)+(-2F\times 1.23)$

$\Delta G_3^0=(-2\times 96500\times 0.44)+(-2\times 96500\times 1.23)$

$\Delta G_3^o=-322310J$

$\therefore \Delta G_3^o=-322kJ$