This question is about redox, electrode potentials and feasibility.
| Redox system | Equation | E∘/VE^{\circ}/\text{V}E∘/V |
|---|---|---|
| 1 | Cd2+(aq)+2e−⇌Cd(s)\text{Cd}^{2+}(\text{aq}) + 2\text{e}^- \rightleftharpoons \text{Cd}(\text{s})Cd2+(aq)+2e−⇌Cd(s) | −0.40-0.40−0.40 |
| 2 | H2SO3(aq)+4H+(aq)+4e−⇌S(s)+3H2O(l)\text{H}_2\text{SO}_3(\text{aq}) + 4\text{H}^+(\text{aq}) + 4\text{e}^- \rightleftharpoons \text{S}(\text{s}) + 3\text{H}_2\text{O}(\text{l})H2SO3(aq)+4H+(aq)+4e−⇌S(s)+3H2O(l) | +0.45+0.45+0.45 |
| 3 | Fe3+(aq)+e−⇌Fe2+(aq)\text{Fe}^{3+}(\text{aq}) + \text{e}^- \rightleftharpoons \text{Fe}^{2+}(\text{aq})Fe3+(aq)+e−⇌Fe2+(aq) | +0.77+0.77+0.77 |
| 4 | Cr2O72−(aq)+14H+(aq)+6e−⇌2Cr3+(aq)+7H2O(l)\text{Cr}_2\text{O}_7^{2-}(\text{aq}) + 14\text{H}^+(\text{aq}) + 6\text{e}^- \rightleftharpoons 2\text{Cr}^{3+}(\text{aq}) + 7\text{H}_2\text{O}(\text{l})Cr2O72−(aq)+14H+(aq)+6e−⇌2Cr3+(aq)+7H2O(l) | +1.33+1.33+1.33 |
A standard distinction cell is set up in the laboratory based on redox systems 1 and 3 and the standard cell potential is measured.
(i) Describe the construction of this standard cell, including the nature of the electrodes, solutions (including concentrations), any other essential apparatus needed to complete the circuit, and the standard temperature.
(ii) Predict the standard cell potential of this cell.
From the table, identify:
Construct an overall equation for the predicted feasible reaction between the species in redox systems 2 and 4.
