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Le Chat: Simulations in Chemical Equilibrium
Jon L. Holmes Nancy S. Gettys University of Wisconsin–Madison Madison, WI 53706
A Software Program Included in Advanced Chemistry Collection, 3rd Edition, Special Issue 28, a CD-ROM for Students Le Chat: Simulation in Chemical Equilibrium João C. M. Paiva, Victor M. S. Gil, António Ferrer Correia, Department of Chemistry, University of Porto, R. Campo Alegre 687, 4169-007 Porto, Portugal
Le Chat: Simulations in Chemical Equilibrium is a computer-based graphical illustration of the chemical equilibrium phenomenon, in relation to Le Châtelier’s principle. Le Chat illustrates the movement toward equilibrium for reactions in the gas phase, as well as the changes produced in the equilibrium state by a given perturbation of concentration or partial pressure, temperature, or volume (total pressure). Advanced Chemistry Collection, 3rd edition, includes a new set of exercises using Le Chat for advanced students that was not included in the version of Le Chat published in General Chemistry Collection, 6th edition (1, 2). The basic steps in running Le Chat are choosing a chemical system, setting initial conditions for the system, and running a simulation of the system’s progress to equilibrium. For any chemical system, each substance in the system is represented by a specific color. Color-coding is continued in the chemical formula for the reaction, in the bar-graph representations of the initial and final conditions for the reaction, in all of the plots, and in the reaction simulation area, where colored dots represent molecules of the substance with the corresponding color coding. The number of dots of each color qualitatively reflects the relative concentrations (mole fractions). Le Chat defines a simulation as a plot of concentration or partial pressure versus time for a specific chemical system with given initial conditions. The free energy value is plotted during a simulation and students can watch it change until it reaches zero (at equilibrium). Values for G°, H°, and S° are also shown. A sequence of simulations is defined in Le Chat as a group of simulations for the same chemical system in which each simulation has unique initial conditions. A record of each
simulation that has been performed on the current chemical system is displayed on the screen. Each time a new simulation is performed on the chemical system, a graphical representation of the simulation is placed in a panel on the screen. Users can review a simulation by clicking its panel, print the results of any simulation in the sequence, and delete simulations. The sequence of simulations can also be saved and reloaded later. The on-screen help window provides content sensitive background information concerning Le Châtelier’s principle and the main operation instructions. By default, this area uses components from Internet Explorer and shows information in HTML format. There is also an option to view on-screen help in rich text format (RTF). Students can select from 11 pre-programed equations. You can also add or delete equations or chemical substances. Literature Cited 1. General Chemistry Collection, 6th ed. [CD-ROM]; J. Chem. Educ. Software 2002, SP16. 2. Paiva, J. C. M.; Gil, V. M. S.; Correia, A. F. J. Chem. Educ. 2002, 79, 640.
Le Chat’s main screen.
JChemEd.chem.wisc.edu • Vol. 80 No. 1 January 2003 • Journal of Chemical Education
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