The disproportionation of aqueous copper

CHEMISTRY · Multi-part · A Level · Chemistry · Electrode potentials · Electrode potentials

Problem

The disproportionation of aqueous copper(I) ion under standard conditions is represented by 2 Cu+(aq)→Cu(s)+Cu2+(aq)2\,\mathrm{Cu}^{+}(\mathrm{aq}) \rightarrow \mathrm{Cu}(\mathrm{s}) + \mathrm{Cu}^{2+}(\mathrm{aq}) At 25 ∘C25\,^\circ\mathrm{C} the reaction has a standard molar Gibbs free-energy change of ΔG∘=−65.0 kJ\Delta G^\circ = -65.0\,\text{kJ}. Faraday’s constant: F=9.65×104 C mol−1F = 9.65 \times 10^{4}\,\text{C mol}^{-1}. (a) Determine the standard cell potential associated with the disproportionation reaction. (b) The standard reduction potential for the Cu2+/Cu+\mathrm{Cu}^{2+}/\mathrm{Cu}^{+} half-reaction is E∘=0.15 VE^\circ = 0.15\,\text{V}. Using your result from part (a), calculate the standard reduction potential for the Cu+/Cu(s)\mathrm{Cu}^{+}/\mathrm{Cu}(\mathrm{s}) half-reaction. (c) A galvanic cell is constructed by coupling the Cu+/Cu(s)\mathrm{Cu}^{+}/\mathrm{Cu}(\mathrm{s}) half-cell you found in part (b) with the standard hydrogen electrode (H2(g)/H+(aq)\mathrm{H}_{2}(\mathrm{g})/\mathrm{H}^{+}(\mathrm{aq})). Write the balanced overall cell reaction that proceeds spontaneously and determine the standard cell potential for this galvanic cell. Confirm that the direction you predict is consistent with the sign of the overall ΔG∘\Delta G^\circ.

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