A voltaic cell is assembled using the following cell diagram

CHEMISTRY · Multi-part · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

A voltaic cell is assembled using the following cell diagram, with all solutions at 1.0 M concentration and 298 K temperature. Pt(s) | I

^{-}

(aq), I

_{2}

(s) || Fe

^{3+}

(aq), Fe^{2+}(aq) | Pt(s) Selected standard reduction potentials: Fe

^{3+}

+ e

^{-}

\;\longrightarrow\;

^{2+}

E^{\circ} = +0.77\;\text{V}

_{2}

+ 2 e

^{-}

\;\longrightarrow\;

2 I

^{-}

E^{\circ} = +0.54\;\text{V}

(a) Identify the species that undergo oxidation and reduction when the assembled cell operates spontaneously. (b) Write the balanced overall redox reaction for the spontaneous process, including physical states. (c) Calculate the standard cell potential

E^{\circ}_{\text{cell}}

for the reaction in part (b). (d) Suppose the chemist mistakenly attempted to reverse the cell by forcing electrons to flow in the opposite direction. Predict the sign of the external voltage that would need to be applied and explain how it relates to

E^{\circ}_{\text{cell}}

and thermodynamic favorability.

Related theory

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