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  Home > JCE Print > Journal of Chemical Education > Issues > 2000  > January  >
In the Classroom
The Use of Extent of Reaction in Introductory Courses
Sebastian G. Canagaratna
Department of Chemistry, Ohio Northern University, Ada, OH 45810
Cover
January 2000
Vol. 77 No. 1
p. 52
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.

Supplement
An extended version of the article, sections on stricter notation, and specific treatment in other applications are provided. Note: the pdf link is unavailable at this time.
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*  Citation
 Canagaratna, Sebastian G. J. Chem. Educ. 2000 77 52.
*  Keywords
 Introductory / High School Chemistry; Stoichiometry; Thermodynamics; Nomenclature / Units / Symbols
*  History
 Created:
Last Updated:		 December 9, 1999
August 31, 2005
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