 
van der Waals and Redlich Kwong: Fitting Two Parameter Equations to Gas Data©  
Theresa Julia Zielinski Department of Chemistry, Medical Technology, and Physics Monmouth University West Long Branch, NJ 077641898 United States mail to: tzielins@monmouth.edu  
Abstract  
The Mathcad document given here is a highly annotated application of nonlinear curvefitting for determining the a and b parameters for the van der Waals and RedlichKwonge quations. The document goes through the development of the sum of squares of deviations SSD, applies the Minerr function to minimize the SSD and then uses the Ftest to determine the equation that best represents the data. The determination of the standard deviation of the fitting parameters is done through the explicit construction and inversion of the Hessian matrix. The treatment here is more extensive than found in most texts. References are included. A suggestion is included for students to use to show mastery of the skills learned by using the document. The document is a solution to the problem presented in the play "It's a Gas!" The "It's a Gas" play and instructional materials can also be found at this site. The "It's a Gas" project is one of several contextrich physical chemistry projects being developed by the Physical Chemistry On Line Consortium. This document was created with Mathcad 6.0 Plus. It will work with higher versions of Mathcad but you may need to check the read statement. Be sure to copy the datafile for the calculation in the document.  
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Comments to: Theresa Julia Zielinski, tzielins@monmouth.edu  
©Copyright Theresa Julia Zielinski, 1996. All rights reserved. You are welcome to use this document in your own classes but commercial use is not allowed without the permission of the author.  