On the Web edited by
William F. Coleman Wellesley College Wellesley, MA 02481
Teaching Kinetics Using Excel Peter Loyson Department of Chemistry, South Campus, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth, 6031, South Africa
[email protected] A short course covering problems of increasing difficulty in chemical kinetics explored via Excel spreadsheet exercises is summarized. It is offered as part of a physical chemistry course. This 10-h computer course is offered parallel to the theory covered in the class and allows kinetics to be explored by handson computer work. Students progress at their own rate. At the end of the course, students are examined individually in a 2-h practical examination. The course is ideally suited to small classes, although with good organization and access to large computer laboratories, large classes can be handled. Students generally enjoy the course because it gives them a visual representation of kinetics and at the same time improves their computer skills. Students should have an introductory knowledge of kinetics and Excel spreadsheets and be able to plot straight lines and enter formulas. The course begins with simple straight-line work to confirm the order of a suitable reaction, using data acquired in the laboratory. The oxidation of ethanol by dichromate is studied. Plotting the required graphs for zero, first, and second order allows the students to establish the order of the reaction with respect to the HCrO4- concentration. Next, students determine a missing infinity reading from a series of data using the principle
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Journal of Chemical Education
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of the sum of the squares of the deviations being a minimum for the correct value. The reaction studied here is the hydrolysis of methyl acetate. This is followed by a study of the simultaneous decay of two radioisotopes to determine the individual rate constants. Students then explore several aspects of consecutive first-order reactions: concentration profiles of reactant A, and products B and C versus time for different values of the rate constants k1 and k2 and the time at which B reaches its maximum concentration for a certain k1 and k2 value. Finally, an in-depth study is made of a multistep reaction process exemplified by the successive chlorination of benzene: students use the necessary equations, which can be complex, to calculate concentrations of benzene and the mono-, di-, and trisubstituted chlorobenzenes expressed as ratios with respect to the initial concentration of the benzene. They then plot this fractional concentration versus moles of chlorine consumed per mole of benzene initially present to see the formation of the different species. Supporting Information Available A detailed description of the course and Excel spreadsheets. This material is available via the Internet at http://pubs.acs.org.
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Vol. 87 No. 9 September 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc. 10.1021/ed1005739 Published on Web 07/23/2010
