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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.
Le Chat's main screen.
Literature Cited
- General Chemistry Collection, 6th ed. [CD-ROM]; J.
Chem. Educ. Software 2002, SP16.
- Paiva, J. C. M.; Gil, V. M. S.; Correia, A. F.
J. Chem. Educ. 2002,
79, 640.
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