2026-04-17T05:23:52Zhttps://recercat.cat/oai/request

oai:recercat.cat:2445/1219162025-11-19T20:35:16Zcom_2072_1057col_2072_478796col_2072_478917

00925njm 22002777a 4500 dc Pérez de Benito, Joaquín F. author 2018-04-27T07:49:16Z 2018-04-27T07:49:16Z 2017-01-21 2018-04-27T07:49:16Z The complexation reaction of Cr(III) ion in the presence of a large excess of EDTA does not follow a pseudo-first-order kinetics as sometimes suggested. There are two causes for the deviation from this simple behavior: the involvement of a long-lived intermediate, precluding the application of the steady-state approximation, and the autoinhibition provoked by the release of hydrogen ions from the organic ligand to the medium as the final Cr(III)-EDTA violet complex is formed. Numerical simulations have allowed obtaining for each kinetic experiment the values of two rate constants, k1 (corresponding to the formation of the long-lived intermediate from the reactants) and k2 (corresponding to the formation of the final complex product from the long-lived intermediate), as well as the number of hydrogens liberated per molecule of final complex product formed (Hkin). The results indicate that k1 is associated to a fast step (Ea = 87 ± 4 kJ mol-1) and k2 to a slow step (Ea = 120 ± 2 kJ mol-1), whereas the number of hydrogen ions lies within the range 0 < Hkin < 2 in all the kinetic runs. A mechanism in accordance with the experimental data has been proposed. Crom Reaccions químiques Cinètica química Chromium Chemical reactions Chemical kinetics Two Rate constant kinetic model for the chromium(III)-EDTA complexation reaction by numerical simulations