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  Home > JCE Print > Journal of Chemical Education > Issues > 2002  > April  >
In the Laboratory
Using Limiting-Excess Stoichiometry to Introduce Equilibrium Calculations: A Discrepant Event Laboratory Activity Involving Precipitation Reactions
Stephen DeMeo
Department of Curriculum and Instruction, Hunter College of CUNY, New York, NY 10021
Cover
April 2002
Vol. 79 No. 4
p. 474
Abstract
The transition between limiting and excess stoichiometry and equilibrium calculations is demonstrated in a laboratory activity for introductory college chemistry students. Students are presented with two precipitation reactions and asked to predict the identity of any excess reactants in the filtrate, on the basis of mole calculations they have already learned. They find that in one of the reactions there are two excess reactants instead of only the one that they originally predicted. This "discrepant event" provides a motivating laboratory opportunity in which to introduce the concept of equilibrium, equilibrium calculations, and Ksp as reasonable explanations of the results.
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*  Citation
 DeMeo, Stephen. J. Chem. Educ. 2002 79 474.
*  Keywords
 Equilibrium; Laboratory Instruction; Stoichiometry
*  History
 Created:
Last Updated:		 March 1, 2002
March 16, 2005
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