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  Home > JCE Print > Journal of Chemical Education > Issues > 1999  > May  >
In the Laboratory
Discovering a Change in Equilibrium Constant with Change in Ionic Strength: An Empirical Laboratory Experiment for General Chemistry
Richard J. Stolzberg
Department of Chemistry & Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775-6160
Cover
May 1999
Vol. 76 No. 5
p. 640
Abstract
Students are challenged to investigate the hypothesis that an equilibrium constant, Kc, measured as a product and quotient of molar concentrations, is constant at constant temperature. Spectrophotometric measurements of absorbance of a solution of Fe3+(aq) and SCN-(aq) treated with different amounts of KNO3 are made to determine Kc for the formation of FeSCN2+(aq). Students observe a regular decrease in the value of Kc as the concentration of added KNO3 is increased.
Supplement
The student handout and TA notes can be accessed as a pdf file using Acrobat Reader. The material is also available as two PC documents- one for Word and one for Excel. These documents have been compressed into both a sit file (for Macintosh) and a zip file (for Windows).
*  Contents
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More Information
*  Citation
 Stolzberg, Richard J. J. Chem. Educ. 1999 76 640.
*  Keywords
 Equilibrium; Laboratory Instruction; Aqueous Solution Chemistry; hypothesis testing
*  History
 Created:
Last Updated:		 June 11, 1999
November 22, 2005
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