KINETICS AND MECHANISM OF OXIDATION OF L-ASCORBIC ACID BY CHROMIUM (VI) | ||||
| Al-Azhar Bulletin of Science | ||||
| Article 13, Volume 21, Issue 1-A, June 2010, Page 189-198 PDF (430.96 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/absb.2010.7344 | ||||
 View on SCiNiTO | ||||
| Author | ||||
| MOHAMED A. MANSOUR* | ||||
| Chemistry Department, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt | ||||
| Abstract | ||||
| The kinetics of oxidation of L-ascorbic acid by potassium chromate was studied as a function of pH, L-ascorbic acid concentration and temperature using the spectrophotometric technique. The rate of reaction is first order with respect to the concentration of each reactant and increases as [H+] increases. The kinetic data indicate involvement of the monoprotonated ascorbate species (HA-) in the redox process. A mechanism involving the formation of chromium (VI)- ascorbate intermediate is a rate-determining step followed by a redox step was suggested. The activation enthalpy and activation entropy changes for the reaction have been calculated to be ΔH*= 69 kJmol-1 and ΔS*= -209 JK-1 mol-1, respectively. | ||||
| Keywords | ||||
| Kinetics; Oxidation; L-ascorbic acid; Chromium (VI) | ||||
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