Olaf Runquisf, Rodney Olsen,
Hamline University St. Paul, Minnesota 55104 and Bruce Snadden ~eriot-wattUniversity Edinburgh, Scotland
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Programmable Calculators Simulated experiments
The role of computers in chemical education has been investigated by numerous workers and interesting applications have been reported.' On the other hand, little attention has been given to the potential uses of the programmable calculator. While calculators lack the sophistication and aura of a computer, their low cost, simplicity and large problem solving capabilities2 make them attractive as teaching instruments and worthy of serious consideration. This paper reports the use of a programmable calculator as a data generating system for simulated laboratory experiments. The calculator system employed was the Wang 360 series with a C-P2 Card P r ~ g r a m m e r . ~This system has four random access storage registers (exclusive of processing registers) and a ten digit readout (Nixie tubes). The programmer reads an 80-step punched card. Since the CP-2 card programmer is capable of distinguishing positive and negative numbers, ''looping" and "shunting" operations are possible. For each "experiment" the student is provided with various material which explains briefly the nature and theory of the experiment, describes the procedure for feeding information into the calculator, and suggests a series of questions and/or problems which might be In general computers have been used in three ways: (i) to deliver frames and answers of branched programmed learning (for S., AND LAGO\TSXI, J. J., J. CHEM. example see CASTLEBERRY, S. K., J. CHEM.EDUC.,47, 143 Eouc., 47, 91 (1970); LOWER, J . J., (1970); RODEWALD, L. B., CULP,G. H., A N D LAGOWSKI, J. CHEM.EDUC.,47, 134 (1970)), (ii) as a cornputstianal or search J., J. CHEM.EDUC.,47, 137 instrument (for example see EMMONS, (1970); KIM,H., J. CHEM.EDUC.,47, 120 (1970)) and (iii) to generate data and simulate process- (for example see, RONDEAU, R. E., AND RUSH111, H. A,, J . CHEM.EDUC.,47, 139 (1970); SCHWENDEMAN, R. H., J. CHEM.EDUC.,45, 665 (1968); A. R. EMERY, J. CHEM.EDUC., 42,131 (1965); MORTENSEN, E. M., AND PENICK,R.J., J . CHEM.EDUC.,47, 102, (1970). a BRAESON, G. D., A N D SEEGMILLER, D. W., J . CHEM.EDUC.,47, 117, (1970). Wang Laboratories, Inc., Tewksberry, Mass.
solved. I n all the experiments, the student must make decisions regarding the variables usually controlled by the laboratory worker (i.e., temperature, concentrations, time, etc.). The calculator displays data which is typical of the particular experiment and includes an appropriate amount of "random" error. Following are brief descriptions of two experiments. Titration of an Acid
To "conduct" a simulated titration of a sample of solid acid with sodium hydroxide complete the falloffing steps. (1) Select one pair of several sets of "acid-base titration" program cards and insert the first of the two cards into the card programmer (each pair of cards represents a. different "unknown" acid). (2) Decide what mass of unknown acid is to be titrated, enter this value into the calculator and store it in a storage register. (3) Decide what molarity of NaOH solution shall be used, enter this value into the cslculrttar, and start the card programmer. The calculator displays the pH of the initial solution. (4) Read the pH of the initial solution of acid in 25 ml of water. (5) Place the second card in the card programmer. (6) Decide the total volumeof standard NaOH to be added before a p H reading will he taken, enter thisvalue into the calculator, and start the card programmer. The calculalw displays the pH of the ~esultingsolution. (7) Read the pH of the solution resultingfrom addition of NaOH. (8) Repeat steps 6 and 7 at will.
The student has freedom to choose an "unknown" acid, the sample size, the molarity of NaOH and the increments of base to be added. The calculator displays pH values which include a realistic component of random error (repetitive titrations of the same acid will not give identical results). The plot shown in Figure 1 illustrates typical data from this experiment. The kinds of questions which the student might be asked to solve include the following.
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Figure 1.
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10 15 20 25 30 VOLUME NaOH A D D E D ( M L )
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Tihotion of on unknown acid with sodium hydroxide.
What is the equivalent weight of the acid? What is the pK.7 What sample size should be used for maximum precision and convenience?
Figure 2. Thermal rsorrongsment of ascaridole. Initial consentrotion of ascaridole.0.523 mole/l; 0.T = 1 32'C;O. T = 147.5'C;A.T = 160'C.
Rate Study
equation or concept upon which the programming logic is based is given in the last column. The time required for the student to procure the required data in any of these experiments will vary greatly; simple gravimetric analyses such as experiments 1 and 2, may be "completed" in one or two minutes while a kinetic or equilibrium study (such as experiments 5 or 8) "conducted" a t five or six differenttemperatures may require as long as 15minutes to complete. We believe that simulated experiments such as those described, will provide students with an interesting set of laboratory type problems and a mechanism for exploring the effects of reaction conditions upon a chemical system with a minimum of cost, time, and danger. Teachers may find such experiments useful as prelaboratory exercises, assigned work, enrichment for able students, or a reservoir of data for examination questions. While we certainly do not advocate chemistry courses without laboratory experiences, calculatorsimulated experiments such as those described may prove an acceptable inexpensive "second best" for schools finding it impossible to conduct a laboratory course. We wish to acknowledge the financial assistance of Louis W. and Maud Hill Family Foundation of St. Paul and to thank Wang Laboratories Inc., Tewksbury, Massachusetts for a loan of equipment during part of the work.
To "conduct" a fate study of the thermal rearrangement of ascaridole complete the following steps. (1) Insert the appropriate card into the card programmer. (2) Decide what initial concentration of ascaridole will he used, enter this value into the calculator, and store it in a storage register. (3) Decide the temperature at which the rearrangement will he carried out, enter this value into the calculator, and start the card programmer. (4) Decide a t what time the fust analysis shall be rend (in minutes), enter this value into the cdcnlator and continue the oard programmer The calculator displays product comentratia a1 lime 1. (5) Resd the concentration of product. (6) Repeat steps 4 and 5 at will. (7) The experiment may be repeated using different eoncentre tions (repeat steps 2-5) and/or temperatures (repeat steps 3-5).
Figure 2 illustrates typical data obtained from this "experiment". The kinds of questions students might be asked regarding this experiment include the following. What is the rate equation? What is the rate constant a t 1OO0C? What are the values of E. and AG:? The table lists some representative types of "experiments" which have been prepared along with the variables which can be controlled by the student and the data displayed by the calculator. The fundamental
Some Representative Simulated Experiments for Use with Programmable Calculators* Data Title
Input
1. Fe a n a h i s of an ora aample ( 2 P
Samde No. (50 unique s%mples);
Output
Program Logio
Maas of FexOa
Simple stoiohiometry.
2. C H analysis of an organic odmpound (1)b
aample mass Sample No. (50 unique samples); sample mass
Msas COX: maw Hz0
Simple atoiohlometrv based upon general formula CnHm+an whera n and m are zeneratad bv the
3. Oxidation state of vanadium (2)s
Samde No. (five oxidation statea
V m sample; ml of ' K i n a solution
Simple atomhzometry.
pH of solutions
Equilibrium equations based on oonoentrstions.
Concentration of product
Rate law and Arrhenius equation.
EMF
Nemst eqaation, activity of ions.
Concentration of C a t e~uilibriom % tranmittance
AG = - R T In K
4. Titration of a buffer ( 2 P
5. Kinetic studv of thermal rearranaemen T > 91. molar c o n c m t m t i m ~of NaF; ~ b ( ~ 0 a h Tempersture: initial oancentratlons of A s n d l3 Temperature: initisl concentrations of T and D
a A total of 30 different experiments have been written 0 The number of punched program cards required.
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program.
,
- R T l n K = AH spectrai curves).
- TAS (Gaussian
