Question 8.TE.26: Using the standard electrode potentials given in the Table 8......
Using the standard electrode potentials given in the Table 8.1, predict if the reaction between the following is feasible :
(a) Fe^{3+}(aq) and I^-(aq)
(b) Ag^+(aq) and Cu(s)
(c) Fe^{3+} (aq) and Cu(s)
(d) Ag(s) and Fe^{3+}(aq)
(e) Br_2(aq) and Fe^{2+}(aq).
| Electrode | Electrode reaction | E° (V) | ||
| (Oxidized form + ne^- \longrightarrow Reduced form) | ||||
| F_2| F^- | Strongest oxidizing agent | F _2( g )+2 e^{-} \longrightarrow 2 F ^{-}( aq ) | Weakest reducing agent | 2.87 |
| Co^{3+} | Co^{2+} | Co ^{3+}+e^{-} \longrightarrow Co ^{2+} | 1.81 | ||
| H_2O_2 | H_2O |  |
H _2 O _2+2 H ^{+}+2 e^{-} \longrightarrow 2 H _2 O |  |
1.78 |
| MnO_2, H^+ | Mn^{2+} | MnO _2( s )+4 H ^{+}+2 e^{-} \longrightarrow Mn ^{2+}+2 H _2 O | 1.61 | ||
| Au^{3+} | Au | Au ^{3+}+3 e^{-} \longrightarrow Au ( s ) | 1.50 | ||
| MnO_4^- | Mn^{2+} | MnO _4^{-}+8 H ^{+}+5 e^{-} \longrightarrow Mn ^{2+}+4 H _2 O | 1.49 | ||
| Cl_2 | Cl^- | Cl _2( g )+2 e^{-} \longrightarrow 2 Cl ^{-} | 1.36 | ||
| Cr_2O_7^{2-}, H^+ | Cr^{3+} | Cr _2 O _7{ }^{2-}+4 H ^{+}+6 e^{-} \longrightarrow 2 Cr ^{3+}+7 H _2 O | 1.33 | ||
| O_2, H^+ | H_2O | O _2+4 H ^{+}+4 e^{-} \longrightarrow 2 H _2 O | 1.23 | ||
| Br_2 | Br^- | Br _2(l)+2 e^{-} \longrightarrow 2 Br ^{-} | 1.09 | ||
| NO_3^-, H^+ | NO | NO _3^{-}+4 H ^{+}+3 e^{-} \longrightarrow NO ( g )+2 H _2 O | 0.97 | ||
| Hg^{2+} | Hg_2^{2+} | 2 Hg ^{2+}+2 e^{-} \longrightarrow Hg _2^{2+} | 0.92 | ||
| ClO^- | Cl^- | ClO ^{-}+ H _2 O +2 e^{-} \longrightarrow Cl ^{-}+2 OH ^{-} | 0.89 | ||
| Hg^{2+} | Hg | Hg ^{2+}+2 e^{-} \longrightarrow Hg | 0.85 | ||
| Ag^+ | Ag | Ag ^{+}+e^{-} \longrightarrow Ag | 0.80 | ||
| Hg_2^{2+} | Hg | Hg _2^{2+}+e^{-} \longrightarrow 2 Hg | 0.79 | ||
| Fe^{3+} | Fe^{2+} | Fe ^{3+}+e^{-} \longrightarrow Fe ^{2+} | 0.78 | ||
| MnO_4^- | MnO_4^{2-} | MnO _4^{-}+e^{-} \longrightarrow MnO _4{ }^{2-} | 0.56 | ||
| I_2 | I^- | I _2+2 e^{-} \longrightarrow 2 I ^{-} | 0.54 | ||
| Cu^+ | Cu | Cu ^{+}+e^{-} \longrightarrow Cu | 0.52 | ||
| Cu^{2+} | Cu | Cu ^{2+}+2 e^{-} \longrightarrow Cu | 0.36 | ||
| AgCl |Ag | AgCl +e^{-} \longrightarrow Ag + Cl ^{-} | 0.22 | ||
| Cu^{2+} | Cu^+ | Cu ^{2+}+e^{-} \longrightarrow Cu ^{+} | 0.15 | ||
| AgBr | Ag | AgBr +e^{-} \longrightarrow Ag + Br ^{-} | 0.10 | ||
| H^+ | H_2 | 2H^+ + 2e^- \longrightarrow H_2 | 0.00 | ||
| Fe^{3+} | Fe | Fe^{2+} + 3e^- \longrightarrow Fe | –0.04 | ||
| Pb^{2+} | Pb | Pb^{2+} + 2e^- \longrightarrow Pb | –0.13 | ||
| Sn^{2+} | Sn | Sn^{2+} + 2e^- \longrightarrow Sn | –0.16 | ||
| Ni^{2+} | Ni | Ni^{2+} + 2e^- \longrightarrow Ni | –0.25 | ||
| Fe^{2+} | Fe | Fe^{2+} + 2e^- \longrightarrow Fe | –0.44 | ||
| Cr^{3+} | Cr | Cr^{3+} + 3e^- \longrightarrow Cr | –0.74 | ||
| Zn^{2+} | Zn | Zn^{2+} + 2e^- \longrightarrow Zn | –0.76 | ||
| Al^{3+} | Al | Al^{3+} + 3e^- \longrightarrow Al | –1.66 | ||
| Mg^{2+} | Mg | Mg^{2+} + 2e^- \longrightarrow Mg | –2.36 | ||
| Ce^{3+} | Ce | Ce^{3+} + 3e^- \longrightarrow Ce | –2.48 | ||
| Na^+ | Na | Na^{+} + e^- \longrightarrow Na | –2.71 | ||
| Ca^{2+} | Ca | Ca^{2+} + 2e^- \longrightarrow Ca | –2.87 | ||
| Ba^{2+} | Ba | Ba^{2+} + 2e^- \longrightarrow Ba | –2.91 | ||
| Cs^+ | Cs | Ca^{+} + e^- \longrightarrow Cs | –2.92 | ||
| K^+ | K | Weakest oxidizing agent | K^{+} + e^- \longrightarrow K | Strongest reducing agent | –2.93 |
| Li^+ | Li | Li^{+} + e^- \longrightarrow Li | –3.05 | ||
(a) It is clear from the table that electrode potential Fe^{3+} | Fe (0.77V) is more than that of I_2\ |\ I^- (0.54V), therefore, Fe^{3+} will be readily reduced and the following reaction is feasible.
Fe ^{3+}(a q)+ I ^{-}(a q) \longrightarrow Fe ^{2+}(a q)+\frac{1}{2} I _2(s)
(b) The electrode potential of Ag^+ | Ag (0.80V) is more than that of Cu^{2+} | Cu (0.34V) and therefore, Ag^+ will be reduced by copper. The following reaction is feasible.
2 Ag ^{+}(a q)+ Cu\ (s) \longrightarrow 2 Ag (s)+ Cu ^{2+}(a q)
(c) The electrode potential of Fe^{3+} | Fe (0.77V) is more than that of Cu^{2+} | Cu (0.34V), therefore, Fe^{3+} can be reduced . The following reaction is feasible.
Fe ^{3+}(a q)+ Cu\ (s) \longrightarrow Fe ^{2+}(a q)+ Cu ^{2+}(a q)
(d) The electrode potential of Ag | Ag^+ (0.80V) is more than that of Fe^{3+} | Fe (0.77V) and therefore, Ag^+ will not be reduced by Fe^{3+}. Therefore, the reaction will not be feasible.
Ag (s)+ Fe ^{3+}(a q) \longrightarrow 2 Ag (a q)+ Fe ^{2+}(a q)
(e) The electrode potential of Br | Br^- (1.09V) is more than that of Fe^{3+}\ |\ Fe^{2+} (0.77V) and therefore, Br will be able to reduce by Fe^{3+}. Therefore, the following reaction is feasible.
\frac{1}{2} Br _2(a q)+ Fe ^{2+}(a q) \longrightarrow Br ^{-}(a q)+ Fe ^{3+}(a q)