A galvanic cell operates at with the following half-cells: • | •

CHEMISTRY · Single correct · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

A galvanic cell operates at 298 K298\,\text{K} with the following half-cells: • Cr(s)Cr(s) | Cr3+(1.0 M)Cr^{3+}(1.0\,\text{M}) • MnO4−(0.010 M)MnO_4^{-}(0.010\,\text{M}), Mn2+(1.0 M)Mn^{2+}(1.0\,\text{M}) in acidic solution Compared with the same cell under standard conditions, which statement best describes how the magnitude of the cell potential changes and why? (a) It remains unchanged because concentrations affect only reaction rate, while temperature affects potential. (b) It decreases because Q>1Q>1, so the logarithmic term is positive and the subtraction lowers EE. (c) It increases because the low concentration of MnO4−MnO_4^{-} makes Q<1Q<1, so log⁡Q\log Q is negative and EE rises above E∘E^\circ. (d) It decreases because Q<1Q<1, so log⁡Q\log Q is negative and subtracting a negative value lowers EE.

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