Redox Titration of Ferricyanide to Ferrocyanide with Ascorbic Acid; Illustrofing the Nernsf Equation and Beer-Lambert Law

摘要

Electrochemistry and. the Nernst equation are introduced in the chemistry curriculum at this college during second semester of general chemistry. The electrochemical concepts and applications are discussed further in analytical chemistry, physical chemistry, and biochemistry courses. Considering the prevalence of electrochemical concepts in many areas of chemistry, we feel that it is important that the students understand the fundamental electrochemical concepts early in the chemistry curriculum through hands-on experimentation. In the past, we had problems integrating an experiment that explained the Nernst equation well. For the last two years, we have incorporated a redox titration of ferricyanide ion, [Fe(CN)6]3~, to ferrocyanide ion, [Fe(CN)6]'i"", to show the students how the reduction potential of a redox couple is affected by the concentrations of the redox species, and how they can use the Nernst equation to calculate the standard reduction potential of a half-reaction. While others have reported laboratory experiments dealing with the Nernst equation in this Journal (1-4), these are usually written for more advanced courses such as physical chemistry and instrumental analysis and require techniques (i.e., cyclic voltammetry) that are often beyond the knowledge of typical first-year undergraduate students. In the experiment described here, our students obtain excellent data and we have encountered few problems with this laboratory.