We have developed a simple, resilient experiment that illustrates the Nernst equation and Beer–Lambert law for our second-semester general chemistry students. In the experiment, the students monitor the reduction of ferricyanide ion, [Fe(CN)6]3-, to ferrocyanide, [Fe(CN)6]4-, both electrochemically and spectrophotometrically upon titration with ascorbic acid. The Nernst equation was used to calculate the standard reduction potential of the redox couple at pH 7 and the number of electrons transferred. The standard reduction potential determined experimentally by our general chemistry students corresponds well to the values reported in literature, and the calculated number of electrons transferred between ferricyanide and ferrocyanide was within 5% of one. The dramatic visual observation of the color change during the course of the titration is a major advantage of this experiment.
Supplement
Instructions for the students including a report form and notes for the instructor are available.
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