Spreadsheet titration of diprotic acids and bases

Abstract

CHsCH=CHz+ HCI HCCk +OH RzNCH=CHz + HCI (CH3CHz)zO + BF3 CHz=COCHs + Brz NHs + H z 0 CH3CHO + OHCHsOCHzt + H z 0 CH3CHO + CN CH3COCH3 + Ht CHFCHZ + BrzThese examples were chosen to show that curved arrows always emanate from an e-pair; even though in the case of an n-pair, it may not be written in, the tail of an arrow follows the head of a previous arrow, and while the curved m w s mav be formallv correct. thev are drawn erronmusly lithe; do nor refl4r the chemical propcrtm of the reactants At the beginning of the tutorial the student has the option of reviewing the explanation of the use of curved arrows or of branching to the exercises. At the end of the description of curved arrows, the student can review the material again or continue to the exercises. At the end of each exercise the option to exit the program exists, while at the end of the tutorial one can branch to the beginning of the tutorial or to the start of the exercises. Since the tutorial is protected from wrong key response, it is user friend15 The tutorial entitled CURVARR and written in GWBASIC used as programmer tools from SERAPHIM a machine language routine, BSGRAPH, written by Felino Pascual; a BASIC program, CHR$GEN, authored by Martin Rose; and a well-written documentation, CHR$-GEN.DOC, by James R. Hutchison. The program, which requires 64K memory, a 640 x 200 graphics adapter, MS DOS 2.0 or greater, and GWBASIC 2.02 or greater, runs on IBM compatible clones including the ATT 6300. The program also executes with an EGA or VGA system. A disc copy of the tutorial and documentation is available through SERAPHIM.

Dynamic approach to predict pH profiles of biologically relevant buffers

“…The pH profile of the weak acid upon addition of alkali results in a typical weak acid-base titration curve containing buffering region (where, pH=pK a ) and equivalence point [8] , [2] , [3] . To predict the pH profile of a titration, an analytical equation that relates pH with the concentration of the alkali is necessary [9] . The derivation for such titrations are available in several literatures, text-books and online resources [10] (please refer supporting information).…”

Analysis of Protonation Equilibria of Amino Acids in Aqueous Solutions Using Microsoft Excel

“…Such a quantitative analysis relates a mathematical description and the use of computer software to the experimental data, and therefore, it may significantly improve the understanding of these topics. Graphical simulations of acid–base pH titrations, using a computer spreadsheet, and applications for educational purposes are available. − A theoretical description of titration curves, using a direct single closed-form expression without assumptions and segmentations (dissection of titration curve into two or more segments), is usually problematic since it involves solving a high-order polynomial. , Less complex approaches for data fitting have been proposed that are based on indirect methods using simplified assumptions or functions without direct physical significance. − However, to our knowledge, there are presently no simple tools for students that would combine graphical simulation, theoretical description, and data fitting for amino acid titrations.…”

Facilitating student understanding of buffering by an integration of mathematics and chemical concepts

“…Such an exercise can also provide an opportunity to illustrate important concepts of mathematics that underpin chemistry and biochemistry. Over the past two decades, a number of reports have described the use of computer spreadsheets to provide educational models [3,4] or to enhance titration exercises by providing students with more powerful analyses of the trends and error in the data [5,6]. Other reports have focused on titration from a quantitative perspective and have included graphical analyses, such as the Gran Plot to let students clearly identify the equivalence point during the titration of monoprotic acids [7][8][9] or the Bjerrum Plot to estimate the pK a values of multiprotic acids [10].…”

“…Most biochemistry textbooks feature a plot with volume or equivalents of strong base on the x axis and pH on the y axis [11][12][13][14][15][16][17], whereas at least two texts use pH on the x axis and the amount of strong base on the y axis [18,19]. Similarly, articles in the science education literature present titration plots with amount of strong base on the x axis [5,20] or pH on the x axis [21]. One interesting variation was to focus on "buffering capacity," the plotting of the first derivative of the buffering capacity (⌬ml base/⌬pH) as a function of pH [21].…”