The following redox reaction takes place in a galvanic cell at 298 K: MnO (aq) + 5 Fe…

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

Problem

The following redox reaction takes place in a galvanic cell at 298 K: MnO

_4^{−}

(aq) + 5 Fe

^{2+}

(aq) + 8 H

^{+}

(aq) → Mn

^{2+}

(aq) + 5 Fe

^{3+}

(aq) + 4 H

_2

O(l) Standard reduction potentials (25 °C): MnO

_4^{−}

(aq) + 8 H

^{+}

+ 5 e

^-

→ Mn

^{2+}

(aq) + 4 H

_2

O(l)

E^{\rm o}=+1.51\,{\rm V}

^{3+}

(aq) + e

^-

→ Fe

^{2+}

(aq)

E^{\rm o}=+0.77\,{\rm V}

A student prepares the cathode compartment with 250.0 mL of 6.00 × 10

^{−4}

M MnO

_4^{−}

, 1.50 M H

^{+}

, and 0.0200 M Mn

^{2+}

. The anode compartment contains 1.00 L of a solution that is initially 0.100 M in Fe

^{2+}

and 0.0100 M in Fe

^{3+}

. All species are aqueous unless otherwise noted. (a) Calculate the reaction quotient

Q

for the cell using the initial concentrations. (b) Determine the standard cell potential

E^{\rm o}_{\text{cell}}

for the overall reaction as written above. (c) Compute the actual cell potential under the stated conditions at 298 K. Express the answer with appropriate significant figures and units. (d) Evaluate whether the cell potential would increase, decrease, or remain the same if the H

^{+}

concentration in the cathode compartment were doubled. Justify your answer qualitatively without additional numerical calculation.

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