In a concentration cell, when the 0.05 molar M+ solution is swapped for a 0.0025 molar M+ solution, what is the magnitude of the change in the cell potential?

(A) 35 mV
(B) 70 mV
(C) 140 mV
(D) 700 mV

Correct answer: (B) 70 mV

Solution

For a single-electron electrode, E shifts by 0.059*log(C1/C2). The concentration is reduced by a factor of 20, giving a measurable change in potential.

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