Standard reduction potentials Knowledge-Based Practice

Questions

1. 1.

   Consider the following standard reduction potentials at 298 K: $\text{Pb}^{2+}(aq) + 2e^- \rightarrow \text{Pb}(s) \quad (E^\circ = -0.13\text{ V})$ $\text{Sn}^{4+}(aq) + 2e^- \rightarrow \text{Sn}^{2+}(aq) \quad (E^\circ = +0.15\text{ V})$ $\text{I}_2(s) + 2e^- \rightarrow 2\text{I}^-(aq) \quad (E^\circ = +0.54\text{ V})$ $\text{Fe}^{3+}(aq) + e^- \rightarrow \text{Fe}^{2+}(aq) \quad (E^\circ = +0.77\text{ V})$ $\text{Cl}_2(g) + 2e^- \rightarrow 2\text{Cl}^-(aq) \quad (E^\circ = +1.36\text{ V})$ Under standard conditions, which of the following species can oxidize $\text{Sn}^{2+}(aq)$ to $\text{Sn}^{4+}(aq)$ but cannot oxidize $\text{Fe}^{2+}(aq)$ to $\text{Fe}^{3+}(aq)$?

   • A) $\text{Pb}^{2+}(aq)$
   • B) $\text{Cl}_2(g)$
   • C) $\text{Sn}^{4+}(aq)$
   • D) $\text{I}_2(s)$
2. 2.

   The standard reduction potentials at 298 K are: $\text{Ag}^+(aq) + e^- \rightarrow \text{Ag}(s)$ ($E^\circ = +0.80\text{ V}$), $\text{Ni}^{2+}(aq) + 2e^- \rightarrow \text{Ni}(s)$ ($E^\circ = -0.25\text{ V}$), $\text{Fe}^{2+}(aq) + 2e^- \rightarrow \text{Fe}(s)$ ($E^\circ = -0.44\text{ V}$), $\text{Zn}^{2+}(aq) + 2e^- \rightarrow \text{Zn}(s)$ ($E^\circ = -0.76\text{ V}$), and $\text{Mg}^{2+}(aq) + 2e^- \rightarrow \text{Mg}(s)$ ($E^\circ = -2.37\text{ V}$). In which of the following metal containers can an aqueous 1.0 M $\text{Ni}^{2+}$ solution be safely stored without undergoing a spontaneous reaction?

   • A) A zinc container
   • B) A silver container
   • C) An iron container
   • D) A magnesium container
3. 3.

   Consider the following standard reduction potentials at 298 K: $\text{Br}_2(l) + 2e^- \rightarrow 2\text{Br}^-(aq) \quad (E^\circ = +1.07\text{ V})$ $\text{Fe}^{3+}(aq) + e^- \rightarrow \text{Fe}^{2+}(aq) \quad (E^\circ = +0.77\text{ V})$ $\text{I}_2(s) + 2e^- \rightarrow 2\text{I}^-(aq) \quad (E^\circ = +0.54\text{ V})$ Which of the following redox reactions is thermodynamically spontaneous under standard conditions?

   • A) $2\text{Fe}^{3+}(aq) + 2\text{Br}^-(aq) \rightarrow 2\text{Fe}^{2+}(aq) + \text{Br}_2(l)$
   • B) $2\text{Fe}^{3+}(aq) + 2\text{I}^-(aq) \rightarrow 2\text{Fe}^{2+}(aq) + \text{I}_2(s)$
   • C) $\text{I}_2(s) + 2\text{Fe}^{2+}(aq) \rightarrow 2\text{I}^-(aq) + 2\text{Fe}^{3+}(aq)$
   • D) $\text{I}_2(s) + 2\text{Br}^-(aq) \rightarrow 2\text{I}^-(aq) + \text{Br}_2(l)$
4. 4.

   Consider the following standard reduction potentials at 298 K: $$\text{Ag}^+(aq) + e^- \rightarrow \text{Ag}(s) \quad (E^\circ = +0.80\text{ V})$$ $$\text{Cu}^{2+}(aq) + 2e^- \rightarrow \text{Cu}(s) \quad (E^\circ = +0.34\text{ V})$$ $$\text{Ni}^{2+}(aq) + 2e^- \rightarrow \text{Ni}(s) \quad (E^\circ = -0.25\text{ V})$$ $$\text{Zn}^{2+}(aq) + 2e^- \rightarrow \text{Zn}(s) \quad (E^\circ = -0.76\text{ V})$$ Based on these data, which species is the strongest reducing agent under standard conditions?

   • A) $\text{Ag}^+(aq)$
   • B) $\text{Cu}(s)$
   • C) $\text{Zn}^{2+}(aq)$
   • D) $\text{Zn}(s)$
5. 5.

   Given the standard reduction potentials $\text{Cr}^{3+}(aq) + 3e^- \rightarrow \text{Cr}(s)$ ($E^\circ = -0.74\text{ V}$) and $\text{Cd}^{2+}(aq) + 2e^- \rightarrow \text{Cd}(s)$ ($E^\circ = -0.40\text{ V}$), what is the standard cell potential ($E^\circ_{\text{cell}}$) of a galvanic cell constructed from these two half-cells?

   • A) -1.14 V
   • B) -0.34 V
   • C) +1.14 V
   • D) +0.34 V

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