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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 8 Issue 1 (2008) pp 15-21

Redox Equilibria as a Special Case Within a General Treatment of Aqueous Ionic Reactions: Applications in Electrochemistry

Constantino Fernández-Pereira,* José Vale, and Manuel Alcalde

School of Industrial Engineering. Department of Chemical and Environmental Engineering (DIQA) at the University of Seville, E-41092 Sevilla, Spain,
Received June 27, 2002. Accepted September 18, 2002

Published online: 6 December 2002

Abstract. For the last few years we have been trying to show the advantages of a simplified treatment of ionic equilibria—in which we underscore the commonalities among acid–base, oxidation–reduction, precipitation, and complexation reactions—and also to improve it. In the proposed treatment, the above reactions are seen as the result of a particle exchange between a donor and an acceptor that belong to two different conjugate pairs. This treatment also proposes a graphical method for solving equilibrium problems through the use of predominance diagrams. Though most introductory chemistry courses present ionic equilibria separately, it is of interest pedagogically to generalize and study them jointly as this provides coherence and systematization as well as a global vision of ionic reactions. In this article, the unified treatment is applied to oxidation–reduction equilibria and to the resolution of redox problems. The paper also includes a comparison between the proposed treatment and the traditional method. The proposed procedure only requires the use of two expressions for the calculation of the redox potential, the same two expressions used for calculating the pH in acid–base problems, as a recent paper in this journal showed. This approach seems to satisfactorily meet the teaching objectives of many general chemistry courses as well as some advanced chemistry courses, and it also simplifies some aspects of electrochemistry, such as the cell electromotive force and cell polarity, which are often difficult for students at that level to understand.

Key Words:  In the Classroom; general chemistry; electrochemistry; analytic chemistry;

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Issue date: February 1, 2003

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