Oxidation Number Rules: A Program To Test the Effect of Various Rules on the Assignment of Oxidation Numbers
Thus by using this program, chemically relevant examples surb as the of ammonia f& nit~ngenand hydrogen, ran be introduced into general rhem1str.y without regard to mathematical difficulty.
James P. Birk Arizona State University Tempe. AZ 85287-1604
In developing the inorganic reactivity expert system, PIRExS (21, it was necessary to teach the computer to assign oxidation numbcrs to inorganic compounds 13,. A set of six rules, thosc normally provided to students for oxidation number assignment,^ was used initially. It soon became obvious, however, that this set of rules would not work when interpreted literally by the computer. A major problem with the initial set of rules was the absence of information about the com~ositionand charee of common oxoanions and other pol;atomic ions. For example, compounds containing a metal with a variable oxidation number and a n oxoanion, such as FeS04, could not be assigned oxidation numbers. To provide the computer with enoueh information to reliably &sign oxidationAnumbersto all-our test compounds, i t was necessary to develop a set of 16 major rules, one of which consisted of 12 subrules. Oxidation Number Rules allows an instructor to select any combination from the list of 27 rules and subrules that were taught to the computer. The user can then test the selected set of rules to see which comuounds can be assigned oxidation numbers correctly. The computer will assien oxidation numbers to those elements for which the selected rules apply and indicate those elements that it was unable to assien. In this wav. it is wssible to select a subset of the rulesif students will be expected to assign oxidation numbers only to a subset of inorganic compounds. Depending on the inorganic species, the number of necessary rules can be as few as 6 or as manv as all 27 rules. The program is menu-driven and on-line instructions are available.
Equilibrium Calculator Robert Allendoerfer State University of New York at Buffalo Buflalo, NY 14214-3094 ~
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Equilibrium Calculator,'adaptated from a previously published computer program (41, has the potential to eliminate quadratic equations from general chemistry books as calculators have eliminated logarithm tables. Many current textbooks limit the discussion of the calculation of equilibrium concentrations to a few carefully chosen examples that can be treated using only second order polynomials. for example. PCls + PCL + Cb. because these are the only type of irol;lems that students can solve exactly. Equilibrium Calculator can calculate the eouilibrium concentrations of all the reagents in a n a r b i t r a j chemical reaction with as many as five reactants and products:
without the necessity of solving polynomial equations. The program works by minimizing the Gibbs Free Energy as a function of the extent of reaction using a n iterative algorithm. This method for single step equilibria (5, 6)has been extended to competing and coupled reactions (7). The input data are: 1. The stoichiometric coefficients in the balanced quatian 2. The initial concentrations of the chemical species 3. The equilibrium constant, Kc
126
Journal of Chemical Education
About This Issue John W. Moore Jon L. Holmes University of WisconsikMadison Madison, WI 53706-1396
The four programs that comprise this issue of JCE: Software cover diverse topics in chemistrv. Alkimers addresses one of the very firsi topics encountered by the organic chemistrv student. the identification of the isomers of alkanes. 1t provides the student a n opportunity to learn about the rules and techniaues for naming akanes and to practice what they learn. in addition to simulating firstorder EPR spectra, Electron Paramagnetic Resonance (EPR) Spectrum Simulator's ability to combine spectra makes it an excellent tool for versing the student in the art of deciphering EPR. Oxidation Number Rules puts a shadow of doubt on the currently accepted set of rules used in general chemistry to assign oxidation numbers. By testing the ability of a given set of rules to assign oxidation numbers, both students and teachers can learn a significant lesson in how this topic is learned and taught. With Equilibrium Calculator we now have a simple-to-use, generic tool to calculate equilibrium concentrations for very complex reactions. No longer do such calculations have to be limited to those involving simple quadratic equations. Hardware Requirements Programs in Series B of JCE: Software are designed for IBM PS12, PC, or PC-compatible microcomputers with 640K of RAM and one floppy disk drive. CGAor compatible graphics and PC- or MS-DOS 3.1 or later are also reauired. Akimers requires EGAor better graphics EPR Spectrum Simulator also s u ~ ~ o rEGA t s and VGA graphics: To print spectra requiresAanEpson-compatible graphics printer or an HP-7075 or compatible plotter. Two floppy disk drives or a hard disk drive is recommended but not required. An 80286 or better microprocessor and math coprocessor are recommended to greatly improve the computational speed of the program. Literature Cited ~
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1. Calle, P.; Sanchez, A ; Siem, C. J. Chem SOE. Perkin %ns
2 lSW, 1181: C d e , P;
same%, A,:siem, C.c o r b h y d m t p R - s - ~ iwi.2 ~ 9I., 2. Birk. J.P'PIRExS: Predictinglnolganie Reaeh
