This SIR is an equation solver. It will find the equilibrium state of any system, given its chemical equation, initial concentrations and equilibrium constant.
The computer will infer the form of the reaction quotient, Q, from the equation. It recognizes that solids and pure liquids (if they are so designated in the equation) do not appear in the reaction quotient. This program is very flexible, and consequently you must be careful to ensure that the equilibrium constants are reasonable and consistent with your units of concentration and/or pressure. Presumably you will obtain equilibrium constants from sources such as the Handbook of Chemistry and Physics or your textbook. You may also use arbitrary values if you wish to show the effect on the equilibrium state of changes in the equilibrium constant.
Sixteen reactions are stored in a notebook, as in SIR React. You may add to or edit them.
The main display is organized as a reaction table. Aligned below the
equation are three lines, for initial concentrations, changes and final concentrations.
Entries are not provided for solids or pure liquids; they are presumed to be present in
adequate amounts.
If you click on an initial concentration a keypad will appear. You may use it to enter an initial concentration up to 999,999 (which will be shown as 1.000´ 106). If you enter a negative concentration you will get an error message; click it away and try again.
If you click on the equilibrium constant you will see a keypad that allows exponential entries. You may enter equilibrium constants from 1´ 10-99 to 9999´ 1099.
You may toggle between SOLVE and DON'T SOLVE. It is prudent to leave it in the default, DON'T SOLVE, state until you have entered all of your parameters. If it's on SOLVE, the equilibrium state will be deduced and displayed. All of the changes and final concentrations will be shown.
This SIR is most useful in illustrating Le Chatelier's principle, showing how changes in the amounts of starting materials and in the equilibrium constant affect the equilibrium state. It can also be used to produce exact solutions of the equilibrium equations, in order to evaluate approximations.
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Updated July 17, 2000