ISSN 2738-0971 | eISSN 2738-1013

Smiljana Marković

Faculty of Technical Sciences, University of Priština in Kosovska Mitrovica, Kosovska Mitrovica, Serbia

Articles

Open Access Original Scientific Paper

INFLUENCE OF THE ACIDITY OF THE IODOUS ACID SOLUTION SYSTEM ON THE KINETICS OF THE DISPROPORTIONATION REACTION

Influence of the acidity of the iodous acid (HOIO) solution system on the kinetics disproportionation reaction is examined in aqueous sulfuric acid solution (0.125 moldm-3). The disproportionation reaction rate constants were determined at 285, 291, 298 and 303 K based on data obtained under stationary conditions. The calculated rate constants increase with increasing temperature for different values ​​of iodous acid and iodate concentrations. The average activation energy of 46 kJmol-1 was determined for the chosen temperature interval, by a graphical method. The values ​​of pseudo-equilibrium concentrations of kinetically important and catalytic species H+, H2OI+ i IO3- in the disproportionation reaction were determined for the given experimental conditions based on the equilibrium dissociation reactions of sulfuric and iodous acids in the quasi-stationary state. The estimated values ​​of sulfuric and iodous acid are predominant and higher than the concentration of the protonated ion of H2OI+.

Open Access Original Scientific Paper

KINETICS STUDY OF THE DISPROPORTIONATION OF THE IODOUS ACID IN AQUEOUS SULFURIC ACID SOLUTION

In this paper we reported the kinetics of the disproportionation reaction of iodous acid (HOIO) in aqueous sulfuric acid solutions (0.18 mol/dm3) studied by spectrophotometrical measurements of the absorbance at suitable wavelength. The changes of the absorbance were caused because the absorbing I2 molecule species were generated during the reaction. The disproportionation rate constants are calculated at the temperature range between 285 and 303 K with average values: k285 = (0.90 ± 0.08) dm3mol-1s-1, k291 = (1.10 ± 0.10) dm3mol-1s-1, k298 = (1.30 ± 0.07) dm3mol-1s-1and k303 = (1.50 ± 0.10) dm3mol-1s-1, respectively. The corresponding activation energy was determined, for the chosen temperature interval, by a graphical method. In addition, obtained value of activation energy is Ea = 38 ± 5 kJ/mol. The negative value of Gibbs energy change and other thermodinamical parameters show that is the disproportionation reaction thermodynamically feasible. Keywordsiodous acid;disproportionation reaction;rate constants;activation energy.