World Journal of Chemical Education
ISSN (Print): 2375-1665 ISSN (Online): 2375-1657 Website: Editor-in-chief: Prof. V. Jagannadham
Open Access
Journal Browser
World Journal of Chemical Education. 2014, 2(4), 54-58
DOI: 10.12691/wjce-2-4-2
Open AccessArticle

Extent of Reaction Balances: A Convenient Tool to Study Chemical Equilibria

Juan José Baeza-Baeza1, and María Celia García-Alvarez-Coque1

1Departamento de Química Analítica, Universitat de València, c/Dr. Moliner 50, 46100 Burjassot (Spain)

Pub. Date: December 14, 2014

Cite this paper:
Juan José Baeza-Baeza and María Celia García-Alvarez-Coque. Extent of Reaction Balances: A Convenient Tool to Study Chemical Equilibria. World Journal of Chemical Education. 2014; 2(4):54-58. doi: 10.12691/wjce-2-4-2


The extent of a chemical reaction has received little attention in the early stages of Chemistry teaching, despite allowing a general way to work with chemical reactions and equilibria. In this article, the concepts of extent of reaction and extent of reaction balances are revised and several applications to study the change in the concentrations of the species involved in chemical reactions are described for both single and multiple systems. Extent of reaction balances allow a general treatment that can be applied to problems of diverse complexity involving different types of equilibria, either in the gas phase or in solution (acid-base, complexation, precipitation and redox reactions). This treatment depends exclusively on the reactions stoichiometry and can be taught at several levels, for single or coupled equilibria. Several examples are given, from basic problems adequate for High School Chemistry to problems for College Chemistry.

high school chemistry first- and second-year undergraduate chemical education research / applications of chemistry problem solving aqueous solution chemistry / equilibrium

Creative CommonsThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit


[1]  Atkins P., Jones L., Laverman L., Chemical Principles, 6th edn, W. H. Freeman, New York, 2013.
[2]  Russo S., Silver M. E., Introductory Chemistry, 5th edn, Prentice Hall, Upper Saddle River, 2010.
[3]  American Chemical Society (Middlecamp, C. ed.), Chemistry in Context, 7th edn; McGraw Hill, New York, 2012.
[4]  Murphy B., Horner G., Tarcy D., Bylikink S., IB Chemistry Course Book, Oxford University Press, Oxford, 2014.
[5]  Butler J. N., Ionic Equilibria: Solubility and pH calculations, John Wiley and sons, New York, 1998.
[6]  Ruiz-Angel, M.J., Torres-Lapasió, J.R., García-Alvarez-Coque, C., “The Midpoint Method: a Shortcut Approach to Calculate the pH”, Chem. Educator, 15, 90-99, 2010.
[7]  Burgot, J. L., Ionic Equilibria in Analytical Chemistry, Springer, Heidelberg, 2012.
[8]  Tissue, B. M., Basics of Analytical Chemistry and Chemical Equilibria, John Wiley and sons, Hoboken, 2013.
[9]  Ringbom, A., Complexation in Analytical Chemistry, Interscience, New York, 1963.
[10]  Lagier C., Olivieri A., “Calculation of Solubilities of Carbonates and Phosphates in Water as Influenced by Competitive Acid-Base Reactions”, J. Chem. Educ., 67, 934-936, 1990.
[11]  Michalowski T., “Calculation of pH and Potential E for Bromine Aqueous Solution”, J. Chem. Educ., 70, 560-562, 1994.
[12]  Baeza-Baeza J. J., García-Alvarez-Coque M. C., “Systematic Approach to Calculate the Concentration of Chemical Species in Multi-Equilibrium Problems”, J. Chem. Educ., 88, 169-173, 2011.
[13]  Baeza-Baeza J. J., García-Alvarez-Coque M. C., “Systematic Approach for Calculating the Concentrations of Chemical Species in Multiequilibrium Problems: Inclusion of the Ionic Strength Effects”, J. Chem. Educ., 89, 900-904, 2012.
[14]  Fritz J. J., “Systematic Calculation of Ionic Equilibria”, J. Chem. Educ., 30, 442-444, 1953.
[15]  Wall T.W., Greening D., Woolsey R.E.D., “Solving Complex Chemical Equilibria Using a Geometric-Programming Based Technique”, Oper. Res., 34, 345-355, 1986.
[16]  Cobranchi D. P., Eyring E. M., “Calculating Equilibrium Concentrations by the Continuation Method”, J. Chem. Educ., 68, 40-41, 1991.
[17]  Guiñón J. L., García-Antón J., Pérez-Herranz V., “Spreadsheet Techniques for Evaluating the Solubility of Sparingly Soluble Salts of Weak Acids”, J. Chem. Educ., 76, 1157-1160, 1999.
[18]  Pardue H. L., Odeh I. N., Tesfai T. M., “Unified Approximations: A New Approach for Monoprotic Weak Acid-Base Equilibria”, J. Chem. Educ., 81, 1367-1375, 2004.
[19]  de Levie R., “How to Compute Labile Metal-Ligand Equilibria”, J. Chem. Educ., 84, 136-141, 2007.
[20]  Solaz J.J., Quílez J., “Changes of extent of reaction in open chemical equilibria”, Chem. Edu. Res. Pract., 3, 303-312, 2001.
[21]  Garst J. F., “The Extent of Reaction as a Unifying Basis for Stoichiometry in Elementary Chemistry”, J. Chem. Educ., 51, 194-196, 1974.
[22]  Canagaratna S. G., “The Use of Extent of Reaction in Introductory Courses”, J. Chem. Educ., 77, 52-54, 2000.
[23]  Uribe D., “Solving Chemical Equilibria”, J. Chem. Educ., 75, 1177-1179, 1998.
[24]  Birk T., “Matrix Formulation of Complex Equilibria and Acid-Base Equilibria by Use of the Extent of Reaction”, Chem. Educator, 14, 91-95, 2009.
[25]  Paz-García J. M., Johannesson B., Ottosen L. M., Ribeiro A. B., Rodríguez-Maroto J. M., “Computing Multi-Species Chemical Equilibrium with an Algorithm based on the Reaction Extents”, Comput. Chem. Eng., 58, 135-143, 2013.
[26]  Dumon A., Lichanot A., Poquet E., “Describing Chemical Transformations”, J. Chem. Educ., 70, 29-30, 1993. Computing Multi-Species Chemical Equilibrium with an Algorithm based on the Reaction Extents
[27]  Vandezande J. E., Vander Griend D. A., DeKock R. L., “Reaction Extrema: Extent of Reaction in General Chemistry”, J. Chem. Educ., 90, 1177-1179, 2013.
[28]  IUPAC, Compendium of Chemical Terminology,, 2014
[29]  Croce A. E., “The Application of the Concept of Extent of Reaction”, J. Chem. Educ., 79, 506-509, 2002.
[30]  Weltin E., “Calculating Equilibrium Concentration”, J. Chem. Educ. 69, 393-396, 1992.
[31]  Baeza-Baeza J. J., Pérez-Pla F. F., Data Treatment in Kinetics, Encyclopedia of Analytical Chemistry, John Wiley and sons, New York, 2013.
[32]  Maccà C., “The Formulation of the Electron and Proton Balances Equations for solving Complicated Equilibrium Problems in Redox Titrations”, Fresenius J. Anal. Chem., 357, 229-232, 1997.