table and pocket calculator to solve each prohlem. When a correct answer is given the program advances to the next type of question.

If the answer is wrong, the program displays a message of- fering some help to the user and asks him the partial results of the problem steps. In this way, the user notices where he made the mistake. Then the program shows the correct answer and a short comment for a better understanding of the proh- lem. Then the program gives the user another opportunity to test his knowledge with a similar prohlem.

The program analyzes and evaluates the answers as fol- lows:

1) If the answer is correct, the user gets five points. 2) If the answer is wrong, the program offers assistance. If the

student refuses it, the nroeram disolavs a similar oroblem. Now. . . - . . if the answer is correct, the user gets four points, but if the an- swer is wrong again, the program demands that the student accept the assistance.

If the answer is wrong and the user accepts the assistance given, the program displays two questions related to the problem solution and writes a message. Afterwards, the pro- gram offers assistance again. If the user has detected his error, the program gives the user another chance, randomly making a new prohlem. If the answer is correct, the user now gets three points. If it is wrong, the next question appears on the screen.

When the user has not detected his error with the first as- sistance, the program helps him a second time and permits the user to check the mathematical operation needed for correctly solving his prohlem. Then the program gives a third assistance with a different problem. If the answer is correct the student gets only two points. If it is wrong, the program shows the next question, and so on.

Finally, the program evaluates the points obtained by the student. analvzes them. dis~lavs a message ahout the stoi- , . . - chiometric knowledge of the user, and recommends items that the student should study further.

The program runs on a 16K TRS-80 microcomputer in Level I1 BASIC and is available from the authors at the ad- dress given above. All prompts to the student are in Spanish.

Computer-Generated Safety Quiz Jerome S. Levkov and Upendra maker

lona College New Rochelle. NY 10801

The chemistry department at Iona College has been using a computer-generated safety quiz in its introductory chemistry course. The quiz is interactive with multiple-choice questions selected randomly. The program consists of six sections cor- responding to the following aspects of laboratory safety:

1) Proper lahoratory attire 4) Laboratory Protocol 2) Fire-related procedures 5) First Aid 3) Equipment 6 ) Laboratory technique

Each part has three to five multiple-choice questions for a total of twenty-eight questions. When a student runs the . - - program, a question is randomly selected from section one. The student keys in hisher answer and is immediatelv in- formed as to whether it is correct. An incorrect response re- sults in the correct choice being displayed along with appro- priate additional comments.

The next question is generated from the subsequent section and the process is repeated until the number of questions specified by the instructor have been asked. The program is written so that when additional auestions are called for from n pilrticular section, an unused question will be selected. The student is informed of hisher erode. and n score ot'less than 90 results in a request for the student to reread the general

snt'etv in~idelinrs and 11, take another exam. The student must iuhmit a q u i 7 with a oassinr score to the instructor. \Ye ire1 that the test achieves the following objectives.

1) The student is made aware that safety is a significant part of laboratorv work.

ZJ The. slud&t s tcse~d ro $top and t h ink a h a impomnt napwlr dlahorat~ry xnfety, e.& rhr lorat ion <,I tire e~ tm~pish~r* in rhr laboratory.

3) The student will read the safety guidelines before entering the laboratory.

4) Good safety practices are reinforced.

The program is written in IBM VS Basic and runs on an IBM 4341 Group 2 computer. It bas 679 statements, of which 40 are comments. The promam uses 168K 32-bit memory. Due to the large amount oistorage required by the text material, we plan to alter the program so that the questions will be stored in files. Many of the questions and responses refer to specific features of the chemistry laboratories a t Iona College, but the authors will supply a listing and sample execution upon request. Send requests to Dr. Jerome S. Levkov. Please include a check for $1 made payable to Iona College to cover postage and handling.

FORMULA: A Simulated Experiment in Beginning Chemistry

Victor I. Bendall, H. Powell, and M. Taylor Eastern Kentucky University

Richmond, KY 40475

The percentage compocition of potawum vhlorate can he found in thr lal~oraturs hs heat~ng thesalt and ruuatinr thr weight loss to the totaioxigen content. The resid"e canihen he taken up into water and the chloride content found by ti- tration with silver nitrate.

FORMULA is a computer simulation of such an experi- ment. The oxygen determination requires four weighing5 consisting of an empty tube, the tuhe with added perchlorate, that tuhe with added maneanese dioxide. and finallv the tuhe and its rolltents after heating. This partot the proiram em- uhasizes the use or the modern roo-loadinr hnlance. Students a h o read such a balance incorreit~y or tgose who neglect to interpolate the position of the pointer within the simulated scale will evaluate the weights to less than four decimal places, and their final measured oxygen content will reflect the lower precision of the weighings.-Each user of the program gets a different set of weights to measure, although the calculated oxygen content wilialways be 39.1% if the simulated balance is read correctly.

The second part of the program teaches the student the principles of titration. The sample is prepared by dissolution in water of the residues from the first Dart. followed hv fil-

& ,

tration to remove the insoluble manganese dioxide. The fil- trate is accurately diluted to 100-ml, and 20-ml aliquots are taken for the titration. Each of these operations is demon- strated using animated high-resolution graphics. Silver nitrate is contained in a simulat&l:,O-ml hure:. A n enlarged section of the huret at the liquid lrvrl in shown separately so that the position of the liquid ran he estimated to two decimal places. The initial reading of the huret is unique to every user. The addition of the sil\.er nitrate can he wntndled with the naddle.

~ ~ .~~~~~~~~~~ At the equivalence point, the liquid in the flask becomes pink (from blue) and the huret is read again. The titration can he repeated using a fresh 20-ml aliquot of the sample solution. In this manner. the student acouires sufficient information to calculate thechlorine conteni of the sample, and since the oxygen content was found in the first part, the potassium content can he found by difference.

There are several ways in which FORMULA can he utilized. It can he given to individual students to replace a routine laboratory exercise. Students who fail to attend a scheduled

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