Titration Curve for a Programmable Pocket Calculator A titration curve program has been written for use with a TI-58 or TI-59 programmable pocket calculator. The pH of any point on the titration curve for a weak acid titrated by a strong base or a weak base titrated by a strong acid may be calculated using this program. Theconcentration of the initial reagentsand thevolumes are entered along withK,, and the hydrogen ion concentration is automatically calculated for that point. The [H+] calculated for the weak acid witbno titrant is a first approximation. The calculation can be continued by causing the calculator to reiterate until it converges on the same value that one would achieve by working theqnadratie equation (less than 15 sec). The initial points and last pointsin the buffer region of the titration curve also present calculation difficulties. As a consequence, the program has been written so that a decision is made concerning the quantity of titrant added. If it is sufficiently small, the program approximates the hydrogen ion concentration as if only a weak acid were present andgoes through successive loopsusing the hydrogen ion equilibrium concentration correcting for hydrolysis and undergoes ten successive approximations. This requires about 45 sec for ten iterations. If a t this time the numbers that temporarily flash are divergent, the instrument can he nudged intoundergoing another ten reiterative steps, and this may be repeated until a more accurate hydrogen or hydroxide ion concentration is obtained. All points on the titration curve are covered by this program, and i t is quite useful for generating data points in the classroom, laboratory or a tutoring session. Copies of the program and instructions may be obtained upon request. This program was presented a t Chem Ed 18, The Fifth Biennial Chemical Education Conference, Chemical Education Division, American Chemical Society, July 24-28,1978, Colorado State University, Fort Collins, Colorado. University of Southern Mississippi Box 8273 Southern Station Hattieshurg, 39401
Howard P. Williams
Volume 56, Number 4, April 1979 / 237
