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  Home > JCE Print > Journal of Chemical Education > Issues > 1999  > January  >
In the Classroom
Amounts Tables as a Diagnostic Tool for Flawed Stoichiometric Reasoning
John Olmsted III
California State University, Fullerton, Department of Chemistry & Biochemistry, Fullerton, CA 92834-6866
Cover
January 1999
Vol. 76 No. 1
p. 52
Abstract
A table of amounts listing initial concentrations, changes in concentration, and concentrations at equilibrium is a standard feature of general chemistry equilibrium calculations. Amounts tables can also be used to organize the data and reasoning involved in limiting-reagent problems. In this context, amounts tables can provide useful diagnostic information about students' abilities to reason stoichiometrically. As an illustration, second-semester general chemistry students were given a diagnostic test requiring them to construct an amounts table for a simple limiting-reagent problem. The test question had simple but not 1:1 stoichiometry, and the starting amounts were chosen so that the reactant present in larger amount was limiting. Fewer than half the students showed a good grasp of stoichiometric reasoning using amounts tables, despite having successfully completed first-semester general chemistry and having access to a text that presented amounts tables as a stoichiometric tool. About half the weak students showed some ability to reason stoichiometrically but made errors that indicated an imperfect understanding. The others showed nearly complete ignorance of how to reason stoichiometrically. The entries in amounts tables also made it clear that some students adopt algorithms as a way of "solving" stoichiometry problems without any understanding of the proper application of such algorithms.
More Information
*  Citation
 Olmsted, John A., III. J. Chem. Educ. 1999 76 52.
*  Keywords
 Teaching / Learning Aids; Teaching/Learning Theory/Practice; Stoichiometry
*  History
 Created:
Last Updated:		 June 15, 1999
June 22, 2005
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