$\frac{2}{3} Al_2 O_3 \rightarrow \frac{4}{3} Al + O_2$
$\Delta _rG = + 960\, kJ\, mol^{-1}$
$500^oC$ તાપમાને એલ્યુમિનિયમ ઓકસાઈડ $(Al_2O_3)$ ના વિદ્યુતવિભાજય રીડકશન માટે પોટેન્શિયલમાં જરૂરી ઓછામાં ઓછો તફાવત........ $V$ છે.
at cathode $\left[\mathrm{Al}^{3+} \rightarrow \mathrm{Al}+3 \mathrm{e}^{-}\right] \times 4$
Net reaction
$4 \mathrm{Al}+6O^{2-} \rightarrow 3O_{2}+4 \mathrm{Al}$
$\frac 43 A l+2O^{2} \rightarrow O_{2}+\frac 43 A l$
$n=\frac {12}3=4$
$\Delta G^{\circ}=-n F E^{\circ}$
$\Delta \mathrm{G}^{\circ}=+960 \mathrm{kJ} \mathrm{mol}^{-1}$
$=960 \times 1000 \mathrm{J} \mathrm{mol}^{-1}$
$n=4$
$\mathrm{F}=96500$ Coulomb
$960 \times 1000=-4 \times 96500 \times E^{\circ}$
$E^{\circ}=-\frac{960000}{4 \times 96500}$
$=-2.48 \mathrm{V}$
potential difference $\approx 2.5 \mathrm{V}$
$Zn^{2+}(aq) + 2e^{-} $ $\rightleftharpoons$ $ Zn (s)$ , $E^o_{RP}= -0.762\, V$,
$Cr^{3+}(aq) + 3e^{-} $ $\rightleftharpoons$$ Cr(s)$, $E^o_{RP} = -0.740\, V$
$2H^{+}(aq) + 2e^{-} $$\rightleftharpoons$$ H_2(g)$, $E^o_{RP} = 0.00\,V$,
$Fe^{3+}_{(aq)} + 2e^{-} $$\rightleftharpoons$$ Fe^{2+}(aq)$ , $E^o_{RP} = 0.77 \,V$
$Fe^{+2} + Zn \rightarrow Zn^{+2} + Fe$
$Zn \rightarrow Zn^{+2} + 2e^{-}$ અને $E^{0} = 0.76$ વૉલ્ટ,
$Fe \rightarrow Fe^{+2} + 2e^{-}$ અને $E^{0} = 0.41 $વૉલ્ટ
આપેલ $\left( E _{ Cu ^{2+} / Cu ^{+}}^{0}=0.16 V \right.$ $,E _{ Cu ^{+} / Cu }^{0}=0.52 V,$ $\left.\frac{ RT }{ F }=0.025\right)$