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Kinetics and mechanism of chromic acid oxidation of oxalic acid in absence and presence of different acid media. A kinetic study
Author(s) -
Khan Zaheer,
Hashmi Athar A.,
Ahmed Lateef,
Haq M. M.
Publication year - 1998
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1998)30:5<335::aid-kin3>3.0.co;2-t
Subject(s) - oxalic acid , chemistry , oxidizing agent , kinetics , inorganic chemistry , reaction rate constant , rate determining step , reaction mechanism , reaction rate , chromic acid , catalysis , nuclear chemistry , organic chemistry , physics , quantum mechanics
Kinetics and mechanism of the reaction of Cr(VI) with oxalic acid have been studied in presence and absence of H 2 SO 4 , HClO 4 , and CH 3 COOH by monitoring the formation of Cr(III)‐oxalic acid complex at 560 nm. The effect of total [oxalic acid], [Cr(VI)], [H 2 SO 4 ], [HClO 4 ], and [CH 3 COOH] on the reaction rate was determined at 30°C. Formation of carbon dioxide was also confirmed. The oxidation rate increases with [oxalic acid] and [CH 3 COOH] while it decreases with [H 2 SO 4 ], [HClO 4 ], and pH. The rate law governing the oxidation of oxalic acid over a wide range of conditions is rate= k 1 K es1 [oxalic acid] T [Cr(VI)] T 1+ K es1 [oxalic acid] T , where only undissociated oxalic acid is kinetically active. Kinetic evidence for the formation of a Cr(VI)(SINGLEBOND)oxalic acid 1:1 complex has been obtained and the equilibrium constant for their formation has been determined. The 1:1 complex exists most likely in an open chain form. The rate‐limiting step of the oxidation reaction involves the breaking of the C(SINGLEBOND)C bond in the 1:2 complex. Oxidizing ability of Cr(VI) species have been discussed. Mechanism with the associated reaction kinetics is assigned. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 335–340, 1998