Which of the following reactions are feasible, if the electrode potential are

${{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{I}}_2/{\mathrm{I}}^{-}}=0.54 \mathrm{V},{{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}=0.77 \mathrm{V},{{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}=0.8 \mathrm{V}$ $\text{ and }{{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}=0.34 \mathrm{V}$

 

For a reaction to be feasible, ${{\mathrm{E}}^{\mathrm{o}}}_{\text{cell }}$ must be positive and

$\text{ (a) }{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)\text{ and }{\mathrm{I}}^{-}\left(\mathrm{aq}\right)$

(a) Oxidation half-reaction

$2\mathrm{\Gamma }\left(\mathrm{aq}\right)⟶{\mathrm{I}}_2\left(\mathrm{s}\right)+2{\mathrm{e}}^{-};{\mathrm{E}}^{\mathrm{o}}=-0.54 \mathrm{V}$

Reduction half-reaction

$2{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}⟶2{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right); \mathrm{E}°=+0.77 \mathrm{V}$

Overall reaction,

$2{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+2\mathrm{I}\left(\mathrm{aq}\right)⟶2{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)+{\mathrm{I}}_2\left(\mathrm{s}\right)$

$\mathrm{E}°=+0.23 \mathrm{V}$

Positive Emf indicates that the reaction is feasible.

(b) Oxidation half reaction,

$\mathrm{Cu}\left(\mathrm{s}\right)⟶{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-};\mathrm{E}°=-0.34 \mathrm{V}$

Reduction half reaction,

$2{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}⟶2\mathrm{Ag}\left(\mathrm{s}\right);\mathrm{E}°=+0.80 \mathrm{V}$

Overall reaction,

$\mathrm{Cu}\left(\mathrm{s}\right)+2{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)⟶{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2\mathrm{Ag};\mathrm{E}°=+0.46 \mathrm{V}$

Positive emf indicates that the reaction is feasible.

(c) Oxidation half-reaction,

$\mathrm{Cu}\left(\mathrm{s}\right)⟶{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-};\mathrm{E}°=-0.34 \mathrm{V}$

Reduction half-reaction,

$\left.{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+{\mathrm{e}}^{-}⟶{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)\right]\times 2;\mathrm{E}°=+0.77 \mathrm{V}$

Overall reaction,

$\mathrm{Cu}\left(\mathrm{s}\right)+2{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)⟶{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)$

                                           $\mathrm{E}°=+0.43 \mathrm{V}$

Positive emf indicates that the reaction is feasible.

(d) Oxidation half-reaction,

$\mathrm{Ag}\left(\mathrm{s}\right)⟶{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{e}}^{-};\mathrm{E}°=-0.80 \mathrm{V}$

Reduction half-reaction,

${\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)+{\mathrm{e}}^{-}⟶{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right); \mathrm{E}°=+0.77 \mathrm{V}$

Overall reaction,

$\mathrm{Ag}\left(\mathrm{s}\right)+{\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right)⟶{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right);\mathrm{E}°=-0.03 \mathrm{V}$

Negative emf indicates that the reaction is not feasible.