A Simple Method for the Consecutive Determination of Protonation Constants through Evaluation of Formation Curves

Autor/inn/en	Hurek, Jozef; Nackiewicz, Joanna
Titel	A Simple Method for the Consecutive Determination of Protonation Constants through Evaluation of Formation Curves
Quelle	In: Journal of Chemical Education, 90 (2013) 5, S.604-608 (5 Seiten)Infoseite zur Zeitschrift PDF als Volltext Verfügbarkeit
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	0021-9584
DOI	10.1021/ed300172a
Schlagwörter	Science Instruction; College Science; Chemistry; Computer Uses in Education; Equations (Mathematics); Scientific Concepts; Science Experiments; Computation; Intervals + Suchen Sie Ihr Suchwort? Teaching of science; Science education; Natural sciences Lessons; Naturwissenschaftlicher Unterricht; Chemie; Computernutzung; Equations; Mathematics; Gleichungslehre
Abstract	A simple method is presented for the consecutive determination of protonation constants of polyprotic acids based on their formation curves. The procedure is based on generally known equations that describe dissociation equilibria. It has been demonstrated through simulation that the values obtained through the proposed method are sufficiently consistent with the actual values. In contrast with the universally known and applied Bjerrum's method, no differences in the accuracy of determination of subsequent protonation constant values are observed. The proposed method requires the value of one of the protonation constants (e.g., of the first one, K [subscript 1] of the polyprotic acid. An iterative method is proposed for finding the value, starting from approximate values determined from the environment of point "n-bar" = 0.5("n-bar"-average degree of protonation). Apart from high accuracy, the proposed method also has didactic advantages because it illustrates the problem of multiple acid equilibria in a visual (almost graphic) manner. The proposed method may also provide initial constant values for numerical methods of nonlinear approximation of the formation curve. (Contains 3 figures and 4 tables.) (As Provided).
Anmerkungen	Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail: eic@jce.acs.org; Web site: http://pubs.acs.org/jchemeduc
Erfasst von	ERIC (Education Resources Information Center), Washington, DC
Update	2017/4/10