Keywords
Oxidation state
Electron transfer
Reducing agent
Oxidizing agent
Nernst equation
Electrochemical cells
Standard electrode potentials
Reference electrodes
Formal potentials
How to Cite
Abstract
The chemical reactions occuring with electron transfer are known as oxidation-reduction reactions, oxi-reduction reactions or, simply, redox reactions. The loss or gain of electrons is formally indicated by the variation in the oxidation number of the species involved in the process. This electron transfer can occur directly from the donor to the acceptor agent, through close contact between the reactive species, or through indirect electron transfer. To understand how these chemical systems work, one must know the functioning of an electrochemical cell and the Nernst equation, with all its implications. These are the central themes of this didactic article.
References
- International Union of Pure and Applied Chemistry - IUPAC. Grandezas, Unidades e Símbolos em Físico-química – Green Book, p.54, 2018. A tradução para o Português da 3ª edição em inglês, realizada pelas SBQ e SPQ está disponível em: http://www.sbq.org.br/livroverde/
- International Union of Pure and Applied Chemistry - IUPAC. Compendium of Analytical Nomenclature: Definitive Rules - Orange Book, 3rd ed., Blackwell Science Ltd., Oxford, Cap. 8, 1997. Também disponível em: http://media.iupac.org/publications/analytical_compendium/
- International Union of Pure and Applied Chemistry - IUPAC. Compendium of Chemical Terminology - Gold Book, 1987. A versão atualizada até julho de 2019 está disponível em: https://goldbook.iupac.org/
- Referência [1], p. 74-80.
- Andrade JC de. Química analítica básica: equilíbrios iônicos em solução aquosa. Rev. Chemkeys [Online], 2009, 9(3):1-13. Disponível em:
https://econtents.bc.unicamp.br/inpec/index.php/chemkeys/article/view/9647 doi: 10.20396/chemkeys.v1i0.9647
- Vogel AI. Análise Química Qualitativa, Editora Mestre Jou, São Paulo, SP, p.235, 1981.
- Petrucci RH, Harwood WS, Herring FG. General Chemistry - Principles and Modern Applications, 8th ed., Prentice Hall, New Jersey, Chap. 21, 2002.
- Keszei E. Chemical Thermodynamics - An Introduction, Springer-Verlag, Berlin, Chap.9, 2012.
- Harvey D. Electrochemical Methods of Analysis, IN: Modern Analytical Chemistry, McGraw-Hill, Chap.11, 2000.
- Harris DC. Análise Química Quantitativa, 7ª ed. LTC, Rio de Janeiro, RJ, Cap14, 2008.
- Faraday M. https://pt.wikipedia.org/wiki/Michael_Faraday - acessado em 15 de outubro de 2020.
- Nernst WH. https://pt.wikipedia.org/wiki/Walther_Nernst - acessado em 15 de outubro de 2020.
- Lefrou C, Fabry P, Poignet J-C. Electrochemistry - The Basics, With Examples, Springer-Verlag, Berlin, Chap. 3, 2012.
- Stumm W, Morgan JJ. Aquatic Chemistry – An Introduction Emphasizing Chemical Equilibrium in Natural Waters, 2nd ed. John Wiley & Sons, 780 pp, 1981.
- Daniell JF. https://en.wikipedia.org/wiki/John_Frederic_Daniell - acessado em 15 de outubro de 2020.
- https://glossary.periodni.com/dictionary.php?en=daniell
- Baccan N, Andrade JC de, Godinho OES, Barone JS. Química Analítica Quantitativa Elementar, 3ª ed. revisada, 5ª reimpressão, São Paulo, Editora Edgard Blucher, 2008.
- Bastos ACLM, Rodrigues SEM, Souza JPI. Físico-Química, Universidade Federal do Pará, Cap.8, 2011. Disponível em https://livroaberto.ufpa.br/jspui/handle/prefix/145
- https://glossary.periodni.com/dictionary.php?en=standard+hidrogen+electrode
- Biegler T, Woods R. The Standard Hydrogen Electrode: a misrepresented concept, J. Chem. Educ., 1973, 50: 604-605.
- Trasatti S. The absolute electrode potential: an explanatory note (recommendations 1986), Pure & Appl Chem., 1986, 58:955-966.
- Standard Reduction Potentials at 25°C. CRC Handbook of Chemistry and Physics, 84th edition, 2004. Disponível em: https://saylordotorg.github.io/text_general-chemistry-principles-patterns-and-applications-v1.0/s33-appendix-e-standard-reduction-.html
- Marconato JC, Bidóia ED. Potencial de eletrodo: uma medida arbitrária e relativa, Química Nova na Escola, 2003, 17: 46-49.
- https://glossary.periodni.com/glossary.php?en=silver%2Fsilver-chloride+electrode
- https://glossary.periodni.com/glossary.php?en=calomel+electrode
Outras referências didáticas
- Sanderson RT. On the significance of electrode potentials, J. Chem. Educ., 1966, 43: 584-586.
- Arevalo A, Pastor G. Verification of the Nernst equation and determination of a standard electrode potential, J. Chem. Educ., 1985, 62: 882-884.
- Worley JD. A simple platinum electrode, J. Chem. Educ., 1986, 63: 274-275.
- Lanza P. What does it mean? Reflections on concentration, activity, and electrode potential, J. Chem. Educ., 1995, 72: 1009-1010.
- Ilie Fishtik I, Berka, LH. Procedure for decomposing a redox reaction into half-reactions, J. Chem. Educ., 2005, 82: 553-557.
- Eggen P-O. A simple hydrogen electrode, J. Chem. Educ., 2009, 86: 352-354.
- Vidal-Iglesias FJ, Solla-Gullón J, Rodes A, Herrero E, Aldaz A. Understanding the Nernst equation and other electrochemical concepts: an easy experimental approach for students, J. Chem. Educ., 2012, 89: 936-939.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Copyright (c) 2020 João Carlos de Andrade
