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  Home > JCE Print > Journal of Chemical Education > Issues > 2006  > August  >
In the Laboratory
Principles of Solution Thermodynamics: Demonstration of Nonideal Behavior of Henry's Law. An Undergraduate Laboratory Experiment
Luke Chandler Short and Thorsten Benter
Bergische Universität Wuppertal, Fachbereich C – Naturwissenschaften und Mathematik, , D-42119 Wuppertal, Germany
Cover
August 2006
Vol. 83 No. 8
p. 1233
Abstract
Quantitative analysis of formaldehyde, HCHO, using the Nash reaction has seen a wide application in both the fields of environmental chemistry and medicine. Our group uses portable Nash systems both to monitor trace levels of HCHO (ppbV, 1/109) present in urban air, as well as measure HCHO in urine, an indicator of bladder cancer. Although several techniques are available for the measurement of HCHO, the rugged nature and reliability of modern, off-the-shelf wet chemical monitoring systems places them ahead of other techniques for several applications. Insightful and practical experiments in physical chemistry for the advanced undergraduate laboratory course are possible with this system. Here we discuss a technique to sample both the gas and the liquid phases of a solution of HCHO(aq), permitting the quick and direct determination of the partition coefficient for a nonideal, solute–solvent mixture. Two scenarios are presented to demonstrate factors that influence this thermodynamic ratio: (i) concentration effects and (ii) temperature effects. The goal of this laboratory exercise is to introduce a commonly used type of HCHO analyzer, and then to apply this knowledge to demonstrate nonideal, biphase thermodynamic equilibrium.
Supplement
Instructions for the students and notes for the instructor are available.
*  Contents Folder JCE2006p1233W containing JCE2006p1233W_1.doc and JCE2006p1233W_2.doc (Microsoft Word)
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*  Citation
 Short, Luke Chandler; Benter, Thorsten. J. Chem. Educ. 2006 83 1233.
*  Keywords
 Aldehydes / Ketones; Analytical Chemistry; Atmospheric Chemistry; Environmental Chemistry; Fluorescence Spectroscopy; Graduate Education / Research; Hands-On Learning / Manipulatives; Instrumental Methods; Laboratory Equipment / Apparatus; Laboratory Instruction; Physical Chemistry; Physical Properties; Thermodynamics; Upper-Division Undergraduate
*  History
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Last Updated:		 6/21/2006
6/30/2006
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