World Journal of Chemical Education
ISSN (Print): 2375-1665 ISSN (Online): 2375-1657 Website: http://www.sciepub.com/journal/wjce Editor-in-chief: Prof. V. Jagannadham
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World Journal of Chemical Education. 2020, 8(3), 128-140
DOI: 10.12691/wjce-8-3-5
Open AccessArticle

A Possible Electrochemical Route to a Thermodynamic Redox Reaction Equilibrium Constant in Secondary Education: An Attempt to Come from Science Fiction to Science Education?

Michiel Vogelezang1, and Adri Verdonk2

1Radboud Teacher Academy, Radboud University, Nijmegen, Netherlands

2Chemistry Teacher Education Department, University of Utrecht, Utrecht, Netherlands

Pub. Date: July 30, 2020

Cite this paper:
Michiel Vogelezang and Adri Verdonk. A Possible Electrochemical Route to a Thermodynamic Redox Reaction Equilibrium Constant in Secondary Education: An Attempt to Come from Science Fiction to Science Education?. World Journal of Chemical Education. 2020; 8(3):128-140. doi: 10.12691/wjce-8-3-5

Abstract

A description is given of an electrochemistry refresher course as a basis for tabulated standard electrode potentials using the Nernst equation and relating chemical equilibrium constants. In connection with their professional experiences the participating teachers carried out measurements of the voltage of a self-built electrochemical cell as described in a final examination task. In this task students had to calculate the voltage using tabulated E0 values. The sign of the measured and calculated voltage appeared to be different. Measurement of current-potential curves of different cells with the help of a Poggendorf compensation circuit affirmed the surmise of a thermodynamic context rather than an empirical one for the Nernst equation: reversible reactions have to be distinguished from spontaneous ones. Even the best measuring cells did not give a good correspondence simultaneously for E0 and the factor RT/nF in the Nernst equation, which was not only due to insufficient time to get equilibrium results. This led to the use of cells taken from literature and the concept of activity coefficient calculated from the Debije-Hückel theory. So generalisation (the mathematical form of the Nernst equation), idealisation (very diluted solution), modelling (corpuscularity) and specification (calculation of the activity coefficient) are necessary for a correct interpretation of apparent empirical values like a standard electrode potential or a chemical equilibrium constant.

Keywords:
electrochemistry thermodynamics equilibrium constant activity coefficient Debye-Hückel theory

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