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The Use of Extent of Reaction in Introductory Courses

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Sebastian G. Canagaratna

Department of Chemistry, Ohio Northern University, Ada, OH 45810

J. Chem. Educ., 2000, 77 (1), p 52

DOI: 10.1021/ed077p52

Publication Date (Web): January 1, 2000

Section:

History, Education, and Documentation

Abstract

This article discusses the use of the extent of reaction as an alternative to the traditional approach to stoichiometry in first-year chemistry. The method focuses attention on the reaction as a whole rather than on pairs of reagents as in the traditional approach. The balanced equation is used as the unit of change. The extent of reaction is numerically equal to the number of times the change equivalent to the balanced equation has taken place. The coefficient of a species in the balanced equation represents the change in amount when the balanced equation occurs once. Consequently, the number of times the balanced equation occurs equals the change in amount of i divided by the coefficient of i, and the change in amount of j equals the coefficient of j multiplied by the number of times the balanced equation has occurred. The determination of the limiting reagent is particularly straightforward in this method. The use of extent of reaction in defining molar reaction quantities and rates of reactions is briefly mentioned. Many problems of dimensional correctness of equations are avoided by the use of this method.

I have tried this for the past five years and regard the student response to this method as encouraging.

Keywords (Audience):

High School / Introductory Chemistry

Keywords (Subject):

Stoichiometry

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This article has been cited by 2 ACS Journal articles (2 most recent appear below).

Extents of Reaction, Mass Transfer and Flow for Gas−Liquid Reaction Systems
Nirav Bhatt, Michael Amrhein and Dominique Bonvin
Industrial & Engineering Chemistry Research2010 49 (17), 7704-7717
- Extents of Reaction, Mass Transfer and Flow for Gas−Liquid Reaction Systems
  Nirav Bhatt, Michael Amrhein and Dominique Bonvin
  Industrial & Engineering Chemistry Research2010 49 (17), 7704-7717
  For gas−liquid reaction systems with inlet and outlet streams, this paper proposes a linear transformation of the numbers of moles into five distinct parts, namely, the extents of reaction, the extents of mass transfer, the extents of inlet flow, the ...
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Approaches to the Treatment of Equilibrium Perturbations
Sebastian G. Canagaratna
Journal of Chemical Education2003 80 (10), 1211
- Approaches to the Treatment of Equilibrium Perturbations
  Sebastian G. Canagaratna
  Journal of Chemical Education2003 80 (10), 1211
  Perturbations from equilibrium are treated in the textbooks by a combination of Le Châtelier's principle, the comparison of the equilibrium constant K with the reaction quotient Q,and the kinetic approach. Each of these methods is briefly reviewed. This ...
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