This SIR simulates zero, first and second order reactions. The reacting system is the simplest possible: one mole of reactant makes one mole of product.
Active options are shown in white. You may
increase a quantity by clicking the left mouse button on it, and decrease it by clicking
the right button. On the initial menu you may control the order (0, 1 or 2), rate
constant, initial concentration and the time scale. There is an autoscale facility, which
automatically lets the reaction run three or four half lives (or to completion, for zero
order).
The reaction proceeds, and concentrations are recorded and plotted at intervals. You may interrupt the run at any time, and then restart it. While the reaction is running, a generic spectrum is shown at the left. The "reactant" peak decreases in intensity while the "product" peak grows.
You now have several Plotting options for the data of the run you have just completed.
The Instantaneous Rates option replots the reactant points of the current run and draws a best curve through them. If you now click on the curve (that is, within ten pixels of it) you will see a tangent drawn at that point. The time, concentration and instantaneous rate at that point will be shown on the graph,
This facility shows how the instantaneous rate is measured as the negative slope of the tangent to the curve.
You can compare the instantaneous rate to the concentration at any point on the curve, and deduce the rate law and rate constant.
The remaining options plot C, log(C) and 1/C against time; these are the standard tests for zero, first and second order.
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Updated July 24, 2000