Equilibrium Calculator Robert Allendoerfer State University of New York at Buffalo Buffalo, NY 14214-3094 Equilibrium Calculator, adapted from a previously published computer program (21, has the potential to eliminate quadratic equations fmm 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 polynomiP C ~+ R Clz, because these are the only als,. e.e., - . PC15 . . type of problems that students can solve exactly. Eouilibrium Calculator can calculate the equilibrium concentrations of all the reagents in an arbitrary chemical reaction with as many as five reactants and products: without the necessity of solving polynomial equations. The Dromam works bv minimizing the Gibbs free e n e m as a runldion of the &ent of readion using an iterative algorithm. This method for single step equilibria (3, 4 ) has been extended to competing and coupled reactions (5). The input data are The stoiehiometriccoefficients in the balanced euuation: The initial concentrations of the chemical species; The equilibrinrn ennstmt, K,
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Thus by using this program, chemically relevant examples such as the production of ammonia from nitrogen and hydrogen, . - can be introduced into general chemistry without regard to mathematical difficdty. The program uses the same algorithms and has the same functionality as the previously published DOS version (6). The advantages over the DOS version are those of the Windows interface: integrated mouse support, on-line help files, and the ability to vary screen colors and printer fonts through the use ofan initiation file.
About This Issue John W. Moore Jon L. Holmes University of WiswnsiwMadison Madison, WI 53706-1396 This issue is the first in JCE: Software's new Series D for IBM PSI2 and PC compatibles running Windows. Even though Windows programs can appear in Series B (and two have already (T, 811, the availability of many more has led us to initiate this new software series. Series D's existence indicates the degree to which software is developing and maturing: the software in this first issue gives a good overview of how those developments are proceeding. AnswerSheets by Richard Cornelius is a series of spreadsheet macrosihat allow general-chemistry students toenter their own questions and ubtain answers. An examole is that individualized homework could be asr - - of - - its - ~ use -~ signed and students could later obtain answers to their specific assignment from the computer. AnswerSheets makes effective use of the Windows environment and Microsoft Excel. Promammine in a su~er-hiehlevel language (the spreadshiet) meals that IBM a& Macintosh versions mav be develo~edsimultaneouslv and many difficulties that kight resuit from software and hardware updates will be alleviated. Molecular Dynamics Simulator by Matthews and Heald shows molecular motion in a 32-molecule sample of any ~~~~
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Apprwimate pH, TNe pH. % Dbsoaation vs. Concantratial
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+ % Diss. + pH(ca1c) a pmtrue) Graphs of Equilibrium Calculator results, one of several possible substances. By changing temperature and number density of molecules the solid, liquid, and easeous states can all be shown. Molecular Dvnamics could be used a t the introductory level to provide Gsualization of molecular motions in the three states, or it could be used in more advanced courses where students could exolore ~arameterssuch as tem~erature,number density. .. and type of molecule. Eauilibrium Calculator is a tool that can calculate eauiis librium concentrations for very complex reactions, s i m ~ l eto use. It raises the question whether solving quadraiic equations or interpreting computer-~alculatede~uilibrium concentrations in a variety of related systems is more important for beginning chemistry students. Hardware and Software Requirements Series D of JCE: Software reauires Microsoft Windows version 3.0 or later and associated hardware as defined by Microsoft. We recommend an IBM-PCIAT, PSl2, or compab ible computer with a 80386 or higher processor, a minimum of 4 MB of memory, a hard disk, one floppy disk drive to install the software, and a Windows-compatible graphics card, such as an IBM VGAor a Super VGA adapter with a compatible color monitor, and a mouse. DOS version 5.0 or later is highly recummended. In addition to the hardware and software recommended above, AnswerSheets requires Microsoft Excel version 3.0 or greater. Molecular ~ G a m i c Simulator s benefits greatly from the presence of a math coprocessor, which is highly recommeided. Equilibrium Calculator requires only the software and hardware listed above, but for complicated equilibria may benefit from a math coprocessor. Citations 1. Matthew, G. P Erperimonfd P h y ~ h ICbmhfry: Oxford University Press: New
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2 Campmano. J M l$rll~*tpmaR ..I Comp. Moth Scl. Teorhuw 1881. 10t21.87 3 Wdun. E d Chom EJm 1880.67 7.546. 4 Wr1un.E J Chem N u c . 1891.68,6 ,486
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Journal of Chemical Education
To Order This lssuc Journal of Chemical Education: Software (often called JCE: Software) is a publication of the Journalof Chemical Education. There is an Order Form card inserted in this issue. If this card is not available,contact: JCE: Software,Department of Chemistry, :University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1396; 6081262-5153 (voice);6081262-0361 : (FAX).
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