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  Home > JCE Print > Journal of Chemical Education > Issues > 2000  > September  >
In the Laboratory
An Easy and Fast Experiment for the Determination of the Equilibrium Constants of an Acid-Base Pair, Free and Complexed with a Molecular Receptor
Elena Junquera and Emilio Aicart
Departamento de Química Fisica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040- Madrid, Spain
Cover
September 2000
Vol. 77 No. 9
p. 1215
Abstract
This paper shows a pH-potentiometric technique, an experimental procedure, and a mathematical model, easily affordable in the laboratory, for the simultaneous and fast determination of all the equilibrium constants involved in the competitive association of an acid-base pair substrate with a molecular receptor in aqueous solution. From the dependence of these association constants on temperature (van't Hoff analysis), the change of the enthalpy, DH°, and the entropy, DS°, of the processes can be estimated and discussed in terms of the driving forces governing the interactions.
Supplement
Notes for the instructor and the nonolinear regresion method to determine the equilibrium constant are available.
*  Contents JCE2000p1215W.doc (Microsoft Word); JCE2000p1215W.c (C source code)
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More Information
*  Citation
 Junquera, Elena; Aicart, Emilio. J. Chem. Educ. 2000 77 1215.
*  Keywords
 Equilibrium; Laboratory Instruction; Molecular Recognition; Physical Chemistry; Thermodynamics
*  History
 Created:
Last Updated:		 August 29, 2000
August 31, 2005
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