This SIR is a reaction table spreadsheet, specialized to gas reactions. The top line shows the chemical equation. Aligned under it, the second line shows the starting partial pressures of any gas reagents, the third line the changes, and the last line the final partial pressures.
The computer keeps track of partial pressures and the total pressure
as a reactions proceeds. You have the option of selecting any or all of the pressures, and
the percent completion, to be displayed or to be hidden as the reaction proceeds. This
allows you to illustrate and drill the concept of partial pressures.
From the initial and current total pressures, using the chemical equation, it is possible to deduce all of the partial pressures and the percent completion.
This is an example of a procedure used by nearly all chemists: following a single physical measurement to keep track of the progress of a chemical reaction.
The computer stores up to sixteen equations, which you may edit or replace. It recognises that a formula followed by (s) or (l) represents a non-gas, and it will not include that substance's partial pressure in the calculations.
Before the reaction starts you may enter the initial partial pressures by clicking on each, whereupon a keypad appears. The computer will automatically computer the initial total pressure, and the partial pressures, total pressure and percent reacted as the reaction runs.
You may run the reaction either forward or backward. The computer will warn you if you've made an impossible choice, where there is zero pressure of a gas needed to react.
You may interrupt the reaction at any point, and ask the class to figure out the values of the hidden parameters. During a pause, you may click on hidden parameters to reveal them, or on revealed ones to hide them.
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Updated July 24, 2000