Two galvanic cells, Cell A and Cell B

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

Problem

Two galvanic cells, Cell A and Cell B, are assembled at 298 K using identical platinum electrodes immersed in solutions that contain both

\mathrm{Fe^{3+}}

and

\mathrm{Fe^{2+}}

. The standard reduction potential for the half-reaction

\mathrm{Fe^{3+}}+e^-\longrightarrow \mathrm{Fe^{2+}}

0.77\,\text{V}

. • Cell A:

[\mathrm{Fe^{3+}}]=0.10\,\text{M}

and

[\mathrm{Fe^{2+}}]=1.0\,\text{M}

• Cell B:

[\mathrm{Fe^{3+}}]=1.0\,\text{M}

and

[\mathrm{Fe^{2+}}]=0.10\,\text{M}

Assume no other redox-active species are present and that the volume of each half-cell is the same. (a) For each cell, determine whether the reaction quotient

Q

is greater than, equal to, or less than 1. Justify your answer with reference to the given concentrations. (b) For each cell, indicate whether the cell potential

E

will be numerically greater than, equal to, or less than the standard potential

E^{\circ}

. Provide reasoning that explicitly connects the relative size of

Q

to the magnitude of

E

. (c) Identify which cell has the larger magnitude cell potential. Explain your choice in terms of how far each system is from equilibrium. (d) If both cells are allowed to operate until they reach equilibrium, predict which cell will reach the equilibrium state first. Support your prediction with qualitative reasoning.

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