Acid-Base Titrations, CHM311A Edgar H. Nagel Conduit: The University of Iowa-Oakdale Campus, lowa City, IA 52242 Hardware: Apple I1 family Components: 1 disk and Instructor's Notes Level and Subject: High school or college general chemistry Coot: $75.00.
Summary Ratings: category Ease of Use: Sublen Matter Content: Pedagogic Value: Student Reaction:
Oaad
Average Below average Average I
1
This software might better be titled AcidBase Titration Curves. because that is its sole function. It includes a brief tutorial, defining terms, explaining variables that may be selected, and conclusions which can be drawn and four experimental sections in which a titration curve is graphed "live" for you. The variables which you select are acid and base concentrations, K., indicator, presence or absence of carbon dioxide saturation. and K. values of ~olvorotic ,. acids. The pnkram u c h d be appropriate tor students ~n general chemistry or quantirative analy*is courses. The program is moat apprupriateas enrichment, since the tutorial alone is inadequate t o teach the concepts and the variables with whieh you play would not all be considered core material for a general chemistry level treatment of acid-base titrations. The orief documentation which necompanirs the program iradequate toload and run the program. I'romptu m r sdvanrmg, skrpping ahead, or returning to an earlier section of the program are clear. Some of the answers to questions in the tutorial were awkwardly narrow. For example, to the question
.
"What does K. represent?", it will accept only "ionization constant" or "dissociation constant." "Acidity constant" is not accepted as correct. I t will eventually give you the accepted answer if you persist in writing inappropriate answers, or you can review the tutorial, which is so brief that acceptable answers become obvious when seen again. There were no instructions for program modification. The chemistry involved is accurately used. The experiments for weak acid-strong base titration always begin with thegraphof a strong acid-strong base titration curve and then generate via the live progression of data points the corresponding weak acidstrong base titration curve. The way in which K, of the acid and concentrations hear on practicality of the titration become apparent. Thus the program is strong for developing concepts. However, if you select impractical conditions, you will be able t o will he able see that it leads to error..and vou , to discern the direction ofprror, but there is nothing quanrifatiw about it. The scale of the gmph docs not lend itself to rending volume error, for example. You can "measure" the pH (which is numerically equal t o pK. of the acid) a t the halfway point of a titration by moving a blinking bar upward from pH 1. It movesO.l pH unit per touch of the cursor key, so you can get a result accurate to 0.1 pH unit by counting touches, more accurately than you could read i t off the screen grid. The part about indicator selection does not lead to clear conclusions. A wide range of indicator pK, values all appear to give satisfactory end paints. A student would probably not understand what this section is supposed t o teach. The section on polyprotic acids seems t o presume that a student has actually plotted a titration curve using a pH meter experimentally. This probably will not be true for general chemistry students. The computer's advantage in this soft~~~~
~
ware is to enable the experimenter to try quickly a wide range of acid-base titrations which would take davs of laboratorv work to arcomplirh. On the &her hand, lthoes not really give n student any senae of h
