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KinSimXP is a 32-bit Windows adaptation of a program originally described by
Merrill, Spicer, Brown, and Walling (1) and published
as a software program for MS-DOS (2). It is
also included in JCE Software’s General Chemistry Collection, 6th edition
(3, 4). KinSimXP simulates a chemical
kinetics experiment in which the student investigates the following reversible
reaction:
A + B 
C + D
The objective is to:
- Find the order of reaction with respect to each of the reactants, nA,
nB, nC,
and nD.
- Find the values of the forward and reverse rate constants, kf
and kb, at one or more temperatures.
- Find the values of the forward and reverse activation energies, Ef
and Eb, in kJ/mol.
The isolation method, first devised by W. Ostwald, is used to find the reaction
orders and rate constants. The program provides log and reciprocal plots of the
concentration-versus-time data so that the reaction rates can be determined graphically.
The concentration-versus-time data can also be saved to a file for more sophisticated
data analysis with a spreadsheet or stand-alone statistics program.
The Arrhenius equation is used to find the activation energies. If the kinetic
parameters are determined at more than one temperature, advanced students with
knowledge of physical chemistry can also calculate ΔGT°,
ΔH°, and ΔS° for the overall reaction. The
parameters for the reaction are chosen from 160,000 different sets available,
using a code based on the letters in the “unknown” name.
The mainframe or MS-DOS version of this program was used as a kinetics lab
in the general chemistry program at the University at Buffalo for 25 years, just
as it was originally designed, by analyzing the data according to the Ostwald
method and plotting linearized graphs—log [C] versus time, etc.—to
obtain the rate constants. The precision of the student results was not as good
as it could be, although it is much better than the data students get from their
“real” kinetics labs. It is still used to negate the impression that
nothing works in “real” chemistry labs when it comes to mathematical
data analysis.
Linear least squares (as done by Excel, etc.) is the wrong way to analyze the
data in the presence of significant noise (3). The
error estimates in the kinetic parameters generated by Excel are just plain wrong.
Students get upset when the rate constants and error estimates calculated by Excel
do not give the real result. Doing the graphs by hand from the printouts made
by KinSimXP allows students to get a feel for the accuracy of their results in
the presence of the noise amplified by the linearization process. It gives results
as accurate, though not as precise, as Excel and provides a much more meaningful
laboratory data analysis experience.
In advanced or honors chemistry classes or in physical chemistry, KinSimXP
can be used to generate data for proper analysis by nonlinear curve fitting either
by using a Mathcad template (5) or a commercial statistics
package. KinSimXP generates data that the student can use with whatever data analysis
procedure is appropriate.
The simulation screen in KinSimXP.
Literature Cited
- Merrill, J. C.; Spicer, L. D.; Brown, R.; Walling, C. J.
Chem. Educ. 1975, 52, 528.
- Allendoerfer, R. D. Chemical Laboratory Simulations;
ComPress, a Division of Queue Inc., 1989. Program Kinsim was adapted from a program
described in J. Chem. Educ. 1975, 52, 528 with
permission from J. C. Merrill, L. D. Spicer, R. Brown, and C. Walling, Department
of Chemistry, University of Utah, Salt Lake City, UT. (No longer available.)
- Allendoerfer, R. D.
J. Chem. Educ. 2002, 79, 638.
- General Chemistry Collection, 6th ed. [CD-ROM]; J.
Chem. Educ. Software 2002, SP16.
- Zielinski, T. J.; Allendoerfer, R. D. J.
Chem. Educ. 1997, 74, 1001–1007.
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