(a) The possible reaction between Fe3+(aq) and I–(aq) is $2\mathrm{Fe}^{3+}_{\mathrm{(aq)}} + 2\mathrm{I}^{-}_{\mathrm{(aq)}}$ → $2\mathrm{Fe}^{2+}_{\mathrm{(aq)}} + \mathrm{I}_{2\mathrm{(s)}}$ The above redox reaction can be split into the following two half reactions, Oxidation : $2\mathrm{I}^{-}_{\mathrm{(aq)}}$ → $\mathrm{I}_{2\mathrm{(s)}} + 2e^{-}$ ; $E^{\circ}_{\mathrm{oxi}}$ = –0.54 V ...(i) Reduction : $[\mathrm{Fe}^{3+}_{\mathrm{(aq)}} + e^{-} \rightarrow \mathrm{Fe}^{2+}_{\mathrm{(aq)}}]$ × 2; $E^{\circ}_{\mathrm{red}}$ = +0.77 V ...(ii) Overall reaction : $2\mathrm{Fe}^{3+}_{\mathrm{(aq)}} + 2\mathrm{I}^{-}_{\mathrm{(aq)}}$ → $2\mathrm{Fe}^{2+}_{\mathrm{(aq)}} + \mathrm{I}_{2\mathrm{(s)}}$ ; E° = + 0.23 V Since the EMF for the above reaction is positive, therefore, the above reaction is feasible. (b) The possible reaction between Ag+(aq) and Cu(s) is $\mathrm{Cu}_{\mathrm{(s)}} + 2\mathrm{Ag}^{+}_{\mathrm{(aq)}}$ → $\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2\mathrm{Ag}_{\mathrm{(s)}}$ The above redox reaction can be split into the following two half reactions, Oxidation : $\mathrm{Cu}_{\mathrm{(s)}}$ → $\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2e^{-}$ ; $E^{\circ}_{\mathrm{oxi}}$ = – 0.34 V Reduction : $[\mathrm{Ag}^{+}_{\mathrm{(aq)}} + e^{-} \rightarrow \mathrm{Ag}_{\mathrm{(s)}}]$ × 2; $E^{\circ}_{\mathrm{red}}$ = + 0.80 V Overall reaction : $\mathrm{Cu}_{\mathrm{(s)}} + 2\mathrm{Ag}^{+}_{\mathrm{(aq)}}$ → $\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2\mathrm{Ag}_{\mathrm{(s)}}$ ; E° = + 0.46 V Since the EMF for the above reaction comes out to be positive, therefore, the above reaction is feasible. (c) There are two probabilities for reaction between Cu and $\mathrm{Fe}^{3+}$. The reaction between $\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ and $\mathrm{Cu}_{\mathrm{(s)}}$ occurs according to the following equation (i) $\mathrm{Cu}_{\mathrm{(s)}} + 2\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ → $\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2\mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ The above reaction can be split into the following two half reactions, Oxidation : $\mathrm{Cu}_{\mathrm{(s)}}$ → $\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2e^{-}$ ; $E^{\circ}_{\mathrm{oxi}}$ = – 0.34 V Reduction : $[\mathrm{Fe}^{3+}_{\mathrm{(aq)}} + e^{-} \rightarrow \mathrm{Fe}^{2+}_{\mathrm{(aq)}}]$ × 2; $E^{\circ}_{\mathrm{red}}$ = + 0.77 V Overall reaction : $\mathrm{Cu}_{\mathrm{(s)}} + 2\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ → $\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2\mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ ; E° = + 0.43 V Since the EMF for the above reaction is positive, therefore, the above reaction is feasible. (ii) If the reaction between $\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ and $\mathrm{Cu}_{\mathrm{(s)}}$ occurs according to the following equation, $3\mathrm{Cu}_{\mathrm{(s)}} + 2\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ → $3\mathrm{Cu}^{2+}_{\mathrm{(aq)}} + 2\mathrm{Fe}_{\mathrm{(s)}}$ The EMF of the reaction comes out to be negative, i.e., –0.376 V (– 0.34 V – 0.036 V) and hence, this reaction is not feasible. (d) There are two possibilities for reaction between Ag and $\mathrm{Fe}^{3+}$ ion. (i) If the reaction occurs by following equation, $\mathrm{Ag}_{\mathrm{(s)}} + \mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ → $\mathrm{Ag}^{+}_{\mathrm{(aq)}} + \mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ The reaction can be split into the following two half reactions, Oxidation : $\mathrm{Ag}_{\mathrm{(s)}}$ → $\mathrm{Ag}^{+}_{\mathrm{(aq)}} + e^{-}$ ; $E^{\circ}_{\mathrm{oxi}}$ = – 0.80 V Reduction : $\mathrm{Fe}^{3+}_{\mathrm{(aq)}} + e^{-}$ → $\mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ ; $E^{\circ}_{\mathrm{red}}$ = + 0.77 V Overall reaction : $\mathrm{Ag}_{\mathrm{(s)}} + \mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ → $\mathrm{Ag}^{+}_{\mathrm{(aq)}} + \mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ ; E° = – 0.03 V Since the EMF for the above reaction is negative, therefore, the above reaction is not feasible. (ii) The reaction between $\mathrm{Ag}_{\mathrm{(s)}}$ and $\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ may occur according to the following equation, $3\mathrm{Ag}_{\mathrm{(s)}} + \mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ → $3\mathrm{Ag}^{+}_{\mathrm{(aq)}} + \mathrm{Fe}_{\mathrm{(s)}}$ EMF of this reaction comes to be even more negative i.e., –0.836 V, and hence this redox reaction is also not feasible. (e) The reaction between $\mathrm{Br}_{2\mathrm{(aq)}}$ and $\mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ occurs according to thefollowing equation : $\mathrm{Br}_{2\mathrm{(aq)}} + 2\mathrm{Fe}^{2+}_{\mathrm{(aq)}}$ → $2\mathrm{Br}^{-}_{\mathrm{(aq)}} + 2\mathrm{Fe}^{3+}_{\mathrm{(aq)}}$ The above reaction can be split into the following two half reactions. Oxidation : $[\mathrm{Fe}^{2+}_{\mathrm{(aq)}} \rightarrow \mathrm{Fe}^{3+}_{\mathrm{(aq)}} + e^{-}]$ × 2 ; $E^{\circ}_{\mathrm{oxi}}$ = – 0.77 V Reduction : $\mathrm{Br}_{2\mathrm{(aq)}} + 2e^{-} \rightarrow 2\mathrm{Br}^{-}_{\mathrm{(aq)}}$ ; $E^{\circ}_{\mathrm{red}}$ = + 1.09 V Overall reaction : $2\mathrm{Fe}^{2+}_{\mathrm{(aq)}} + \mathrm{Br}_{2\mathrm{(aq)}}$ → $2\mathrm{Fe}^{3+}_{\mathrm{(aq)}} + 2\mathrm{Br}^{-}_{\mathrm{(aq)}}$ ; E° = + 0.32 V Since the EMF for the above reaction is positive, therefore, the above reaction is feasible.