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  Home > JCE Print > Journal of Chemical Education > Issues > 2005  > November  >
Research: Science and Education
First-Order or Second-Order Kinetics? A Monte Carlo Answer
Joel Tellinghuisen
Department of Chemistry, Vanderbilt University, Nashville, TN 37235
Cover
November 2005
Vol. 82 No. 11
p. 1709
Abstract
In chemical kinetics, data for the concentration [A] as a function of time can be analyzed by least-squares fitting to the appropriate expression for the integrated rate law. The problem of discriminating between first and second order in such analyses is examined through Monte Carlo computational experiments in which synthetic data are fitted to both the direct expressions for [A](t) and to their linearized versions. For 11 data points spanning two half-lives, with 10% random error, a simple comparison of the sum of weighted squared residuals picks the correct order ∼90% of the time, which is better than implied in earlier discussions of this problem. The discriminating ability improves markedly with increasing numbers of data points and reduced experimental error. The article includes a description of procedures that permit students to explore the role of random noise in kinetics data, using the representative data analysis program KaleidaGraph.
More Information
*  Citation
 Tellinghuisen, Joel. J. Chem. Educ. 2005 82 1709.
*  Keywords
 Chemometrics; Computer-Based Learning; Graduate Education / Research; Kinetics; Laboratory Instruction; Physical Chemistry; Rate Law; Upper-Division Undergraduate
*  History
 Created:
Last Updated:		 9/22/2005
9/29/2005
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