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Irreversible Uncatalyzed Reactions
2nd Order (2 Reactants-2 Product)
Description | Equations | Implementation | Examples | Discussion
Examples
To run this model, click on the following parameter file, example1.par. This simulation will allow you to change the initial concentrations of the two reactants, S1 and S2, and to observe the resulting production of the products, P1 and P2. Once the model and the parameter files load, open "Plot_Area 1". Then run the model.
What final concentration of each product is formed? Would you expect this reaction system to produce equal amounts of the two products, or can the system yield unequal amounts of the products? Why? To verify that we in fact get equal amounts of the products, go to "Plot_Area 1" and deactivate the plot of P1. How did the progress curve of this species relate that of the second product, P2? To complete the verification process, deactivate the plot of P2, and then activate the plots of P1 and P2 in that order.
Now vary the initial concentration of S1 between 55 and 100 mM without changing the concentration of S2 and rerun the simulation noting the concentration of products produced in each case. Two or three concentrations of S1 should show you sufficient data to discern a pattern. If you are uncertain of the final product concentration upon examining the graph, the "Report" accessed from the "Plot_Area 1" window gives the output of the simulation in tabular form. Does the amount of product produced vary when altering the concentration of S1 as instructed above? What happens to the concentration of product produced when the initial concentration of S1 is set to 40 mM while the initial concentration of S2 remains at 50 mM? Reduce the initial concentration of S1 to 25 mM and rerun the simulation.
By now, you should have noticed that the concentration of product formed never exceeds the initial concentration of the reactant with the lowest initial concentration, ie., a "limiting reactant" situation.
Total System Concentration
Before we run the simulation again, ask yourself what the total concentration of components in the system (S1, S2, P1 and P2) would be throughout the time of the simulation given the nature of the chemical reaction modeled? Now change the initial concentration of S1 back to 100 mM, and rerun the simulation. Activate the line in "Plot_Area 1" which plots "S1+S2+P1+P2". Did your prediction match the result obtained? Why did the sum of all reactants and products remain constant in the two-product case while it changed in the simulation of the one-product case?
4-2-1-6-1.
Contact John Bassett for comments or questions.
Copyright © 2002 NSR, University of Washington. All rights reserved
Revised 04/22/02