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The Chemical Educator
ISSN: 1430-4171 (electronic version)
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,
pereira@esi.us.es
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;
(*) Corresponding author. (E-mail: pereira@esi.us.es)
Article in PDF format (326 KB) HTML format
Issue date: February
1, 2003
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