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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 4 Issue 6 (1999) pp 206-210

Pedagogic Interest of the H₂O₂, Cu²⁺, SCN^-, OH^- Oscillating Reaction

V. Pimienta and J. C. Micheau*

Laboratoire des IMRCP, UMR au CNRS n° 5623, Université Paul Sabatier, F-31062 Toulouse France

Published online: 1 December 1999

Abstract. Chemical reactivity is generally taught by considering the chemical properties of the reacting entities (acid– base, oxidation–reduction, complexation, and precipitation) and the values of the corresponding equilibrium thermodynamic constants (K_a, E_o, K_d, K_s). This approach, however, is not well- suited to the dynamic chemical systems that are often encountered in industrial and environmental chemistry where nonequilibrium conditions prevail. In this respect, oscillating reactions are a good illustration of the limits of equilibrium thermodynamics and show the need for a complementary dynamic nonequilibrium study. We describe here an oscillating reaction that is easy to carry out in an inorganic chemistry practical class as it uses common reactants (H₂O₂, KSCN, CuSO₄, NaOH). This example should enable students to obtain a more realistic grasp of chemical reactivity based on a comprehension of coupled reaction processes, similar to those encountered in population dynamics or in enzymatic regulation.

Key Words:  In the Classroom; oscillating reaction; industrial chemistry; environmental chemistry; thermodynamics

(*) Corresponding author. (E-mail: micheau@gdp.ups-tlse.fr)

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Issue date: December 1, 1999

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