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  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > August  >
In the Laboratory
A Simplified Method for Measuring the Entropy Change of Urea Dissolution. An Experiment for the Introductory Chemistry Lab
Charles A. Liberko* and Stephanie Terry
Department of Chemistry, Cornell College, Mount Vernon, IA 52314-1098
Cover
August 2001
Vol. 78 No. 8
p. 1087
Abstract
The enthalpy change, equilibrium constant, Gibbs free energy change, and entropy change of the dissolution of urea in water were determined in a guided-inquiry lab experiment. Introductory-level students were able to obtain quite satisfactory thermodynamic values for the dissolution of urea using minimal equipment and a very simple procedure. The enthalpy change of dissolution was determined with a simple coffee-cup calorimeter. Students then directly determined the concentration of a saturated solution of urea simply by measuring the amount of urea used and the total volume of the solution as prepared in a graduated cylinder. The equilibrium expression for the dissolution of urea can be simplified to K = [urea]. With the enthalpy change and the equilibrium constant determined experimentally, the free energy change and enthalpy change for the process are readily calculated.
More Information
*  Citation
 Liberko, Charles A.; Terry, Stephanie. J. Chem. Educ. 2001 78 1087.
*  Keywords
 General Chemistry; Laboratory Instruction; Thermodynamics
*  History
 Created:
Last Updated:		 July 10, 2001
April 14, 2005
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