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ERIC Number: EJ1074511
Record Type: Journal
Publication Date: 2015-Sep
Pages: 5
Abstractor: As Provided
ISSN: ISSN-0021-9584
M[superscript 2+]•EDTA Binding Affinities: A Modern Experiment in Thermodynamics for the Physical Chemistry Laboratory
O'Brien, Leah C.; Root, Hannah B.; Wei, Chin-Chuan; Jensen, Drake; Shabestary, Nahid; De Meo, Cristina; Eder, Douglas J.
Journal of Chemical Education, v92 n9 p1547-1551 Sep 2015
Isothermal titration calorimetry was used to experimentally determine thermodynamic values for the ethylenediaminetetraacetic acid (EDTA)(aq) + M[superscript 2+](aq) reactions (M[superscript 2+] = Ca[superscript 2+] and Mg[superscript 2+]). Students showed that for reactions in a N-(2-hydroxyethyl)piperazine-N"-ethanesulfonic acid (HEPES) buffer (pH = 7.4), the Mg[superscript 2+] + EDTA reaction was endothermic, while Ca[superscript 2+] binding to EDTA was exothermic. EDTA is triply ionized at pH 7.4 and therefore must shed a proton to the buffer prior to chelating the M[superscript 2+] ion; thus the observed reaction enthalpies are strongly dependent on pH and buffer ionization enthalpy.
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:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education; Postsecondary Education
Audience: N/A
Language: English
Sponsor: National Science Foundation (NSF)
Authoring Institution: N/A
Identifiers - Location: Illinois
Grant or Contract Numbers: DUE-0941517