This SIR allows the lecturer and class together to explore the experimental foundations of the law of mass action, the fundamental principle governing chemical equilibrium.
Ten reactions are available, ranging from simple (an isomerization) to complex (formation of ammonia). You may start a reaction with any amount of each reagent, from 0 to 1.5 atm in 0.1 atm increments, and with varying amounts of catalyst. Five temperatures are available for each reaction, chosen to give interesting and informative equilibrium constants. The equilibrium data is thermodynamically accurate.
The uses of this facility are limited only by your imagination and ingenuity. An obvious application is to set up a reaction, choose various starting amounts of reagents, follow the reaction to equilibrium (using lots of catalyst), and challenge the class to find some combination of final amounts that is characteristic of all of the equilibrium states. In this way they can discover the form of the reaction quotient, Q, for increasingly complicated reactions.
The reaction runs for a nominal 18 "minutes", at about one second per "minute". All reagent partial pressures (in atm) are plotted at the end of each minute. You may elect to have the reaction run freely for the full 18 minutes, or you may step through it one minute at a time. The more catalyst, the faster the reaction approaches equilibrium at a given temperature. The amounts are arbitrary, chosen so that with no catalyst a reaction will not reach equilibrium, and with the maximum amount it will get within 1% of equilibrium, in an 18 minute reaction run.
You have the option to show or not show the reaction quotient durubg the reaction
When you select a reaction its equation is displayed above the graph with all partial pressures zero. To alter an initial pressure, simply click the mouse on it. The left button raises the pressure and the right button lowers it. Partial pressures are available between 0 atm and 1.5 atm in 0.1 atm steps.
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Updated July 24, 2000