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JCE WebWare: Web-Based Learning Aids
William F. Coleman Wellesley College Wellesley, MA 02481
Peer-Reviewed JCE WebWare
Edward W. Fedosky University of Wisconsin–Madison Madison, WI 53715
To celebrate the official initiation of the Journal of Chemical Education Digital Library ( JCE DLib), this month we add “Kinetica: An Excel Program To Simulate or Analyze Kinetic Data” to our collection of 20 peer-reviewed WebWare programs. Find this and the entire collection (including 22 programs in open review and 18 Featured Molecules) Only@JCE Online at http://www.jce.divched.org/JCEDLib/ WebWare/. (JCE DLib is part of the National Science Digital Library and is supported by the National Science Foundation.) Kinetica: An Excel Program To Simulate or Analyze Kinetic Data by Leonel Vera, Pedro Ortega, and Miguel Guzmán, Departamento de Química, Facultad de Ciencias, Universidad Católica del Norte, Angamos 0610 Antofagasta-Chile;
[email protected] Keywords: Kinetics, Computer-Based Learning, Spreadsheets Requires: Microsoft Excel 8 (or later) for Windows
Spreadsheets have become valuable tools to simplify and expedite the analysis of complex data for classroom use (1– 6). The Excel spreadsheet Kinetica both simulates and analyzes kinetic data for simple rate equations of the form: −
d[ A] n = k [A ] dt
Instructors or students can generate simulated kinetic data using parameters they specify, or using parameters randomized by Kinetica. The data set that is generated may then be exported for use in exercises, homework, and exams, or may be analyzed directly within Kinetica. A kinetics data set may also be imported from an external source into Kinetica for analysis. Simulated data are obtained using either the Kinetic Data or Games worksheets. In Kinetic Data, the user supplies values for reaction order (n), rate constant (k), initial concentration of A, maximum time duration, time interval, and noise level (a Gaussian perturbation of data). Based on these parameters, Kinetica simulates a kinetics data set, and plots concentration vs. time for this set. The Games worksheet produces a similar output from randomized parameters and stores the values for n, k and t1/2 in a separate worksheet, Games-Results. The data generated may be exported for external use, or may be analyzed within Kinetica.
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Graph from the Scan Orders worksheet showing R 2 plotted vs. Possible Reaction Order.
Analysis of kinetics data is carried out using the Scan Orders and Plots worksheets on data Kinetica has generated or on data supplied from an external source. The Scan Orders worksheet calculates and plots a quadratic correlation coefficient (R 2) vs. possible reaction orders (from n = 0 to n = 5). R 2 is the correlation coefficient between t and Fn([At]), a “concentration function”, equal to ln[A] or [A]1-n for n = 1 or n 1, respectively. When R 2 is plotted against possible reaction orders, the plot’s inverted parabolic shape shows the reaction order with the highest correlation coefficient at the maximum point of the curve; this point corresponds to the mathematically “best” value of n. On the Plots worksheet, Kinetica uses the kinetic data and the chosen best value for n (both taken from the Scan Orders worksheet) to calculate and plot Fn([At]) vs. time. The program displays a best-fit linear trendline with its equation and R 2 value and calculates the corresponding values of k and t1/2. This spreadsheet is intended primarily for use on Windows computers; it may also work on other platforms. Literature Cited 1. Bruist, Michael F. J. Chem. Educ. 1998, 75, 372–375. 2. de Levie, R. J. Chem. Educ. 2000, 77, 534–535. 3. Guiñon, J. L.; García-Antón, J.; Pérez-Herranz, V. J. Chem. Educ. 1999, 76, 1157–1160. 4. Lannone, M. J. Chem. Educ. 1998, 75, 1188–1189. 5. Lo, Glenn V. J.Chem.Educ. 2000, 77, 532–533. 6. Muranaka, K. J.Chem.Educ. 2002, 79, 135.
Vol. 81 No. 1 January 2004
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Journal of Chemical Education
159
