Edited by
John W. Moore Eastern Michigan University Ypsilanti. MI 48197
Bits and Pieces, 2
This is another comnuter-series article devoted to short descriptions of rhemists' applications of computers in their classrwms or latr~ratoriej.Specilk guidelines for writing such short descriptions were puhlished in the April 1YdO issue o i the Journal. 'l'hev can alsu IIP ohtained frtm the computer series editor. MO& authors of Bits and Pieces will make available program listings andlor machine-readable versions. Please read each description carefully to determine compatibility with your own computing environment before requesting materials from any of the authors.
Two Interactive Computer Programs for Quantitative Analysis J a m e s E. Byrd and J o h n T. Burt California State College, Stanislaus Turlock, CA 95380 We will describe two interactive computer-assisted-instruction (CAI) programs that we have developed for use in quantitative anilys~s and in general chemistry: The purpose of the modules is to help students learn to calculate the points along a titration curve for the titration of an acid with a strong hase. EQUIL 1is a tutorial nroeram that interacts with students via a'graphics terminal.'^ rkdomlg generated set of conditions (name of acid, KO,volume, concentrations) is presented, with the major purtim of the pn~graminwlving a step-hy-step calculation of the pH for each volume of hase chosen by the student. As each level of mastery is reached, the dialog becomes less detailed. Studrnt errors, sometimes diagnosed, result in hints to solutions. If the student remains unable to respond correctly, slhe is shown the method of solution and the subsequent dialoi: becomes more detailed again. For those students who come to the terminal without a culculawr, an easily accessed pocket-calculator subroutine is huilt into the program. Its use does nut significantly interrupt the flow of thr dialoe. ". and it nrovides an onnortunitv to reinforce the classroom discussion of significant figures since rounding of the result is necessarv and the comnuter recoenizes errors in significant figures. when the s t u d e k indicates that s h e has done enough calculations to define the titration curve, the computer checks to see if all of the representative types of calculation have been exnlored.. i.e.... ore-eauivalence noint. equivalence point, etc. If some remain untried, the computer suaaests that the student attemot these calculations. The student who is satisfied with h i s h i r mastery can then choose an acid-base indicator for the titration from a library of indicators. The transition range for the chosen indicator is depicted on the titration curve and the consequences of the choice, i.e., titration errors, are determined. If the student chooses, s h e can explore the effect on the titration curve of changing the value of the equilihlium constant and the initial concentration of the acid. The computer plots the theoretical titration curves for the values of K, and the concentration indicated by the student. Two other ontions are incnrnorated in the software. In order to reduce the2'ime that the terminal is occupied, the student can opt t o use the set of conditions for a homework problem.
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Fiaure - 1. Portion of the screen dis~lav . .showlna" student calculated mints 1x1 .. and me computer calculated line for the titration of 25 ml of 0.2 Maceticacid With 0.15 MNaOH. If this route is chosen, the computer makes a copy of the problem automatically on the hard copy unit. When the homework assignment is completed, the stndent can use the second option to check the results of hisher calculations. Reinforcement is provided by a plot of the student-calculated values and the computer calculated curve as well ashy a list of the two sets of values (Fig. 1). The second program, TITRO, is a titration game. This eamine feature ereatlv heiehtens the stndent interest. The u player(~)receive a set of conditions for an acid-base titration. These conditions are randomlv eenerated and are reoresentative of five levels of difficuliyk prediction or calchation of the eauivalence ooints. The object of the game is toadd the volume bf hase needed to reach the equivalence point (within one drop) before your opponent (2 players) or in the fewest moves (1 player). The progress of the titration is presented graphically as a plot of pH versus ml added. This information provides additional clues to the players for their estimation of equivalence-point volumes. (We leave the development of strategies for winning up to those interested in trying the game). Both oroerams are nonular with students. with TITRO ,. finding an avid pool of players among the chemistry faculty as well. Thev are written wine DEC's BASIC-I'I.US and currently run on a DEC PDP fi/45 in a time-sharing environment usine a Tektronix 4014-1 terminal couoled to a 4631 hard copy unk Each program requires 16 K of iser core area. While the eraohics are designed for use on the Tektronix terminal, s&&e changes in the programs would allow their use with terminals having medium resolution graphics capabilities. The programs should run on most systems with only minor modification. Copies of the computer output, a documented listing andlor a listing on your tape (7 track, ASCII, odd parity, 800 BPI, unblocked) are available from the authors. Send a blank tape and a check for $10 (to cover postage and handling) made ~ a v a h l eto: Stanislaus State Colleee Foundation. in care of Dr. james Byrd, Department of ~ k e m i s t r ~~alifornia , State College, Stanislaus, Turlock, California 95380.
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Volume 57, Number 9. September 1980 1 619
