THERMOKINETIC STUDY OF THE ZERO, FIRST AND SECOND ORDER REACTIONS IN A PSEUDO-ADIABATIC CALORIMETER: Numerical approach and experimental dat

• Main Authors: Johanna Mendoza, Oscar Rodríguez Bejarano, Jesús A. Ágreda
• Format: Article
• Language: English
• Published: Universidad Nacional de Colombia 2012-11-01
• Series: Revista Colombiana de Química
• Online Access: http://www.revistas.unal.edu.co/index.php/rcolquim/article/view/30312
• ISSN: 0120-2804; 2357-3791

<div>The signal produced by a pseudo-adiabatic</div><div>calorimeter is simulated by numerical</div><div>solution of the differential equations that</div><div>model the chemical kinetics [1], the thermal</div><div>properties of the calorimetric cell</div><div>[2], and the response of the thermistor</div><div>used as a thermometric sensor [3]. These equations show that the calorimetric</div><div>signal is related with concentration</div><div>in a complex way. Therefore, a comparison</div><div>between the signals of the three</div><div>basic kinetics reactions (zero, first and</div><div>second order) was made, as a first step</div><div>to obtain a standard procedure to follow</div><div>chemical kinetics using a calorimeter. In</div><div>order to help understanding this relationship,</div><div>the initial rate method was applied to the simulated data to assess the relationship</div><div>between the order and the kinetic</div><div>constants calculated with those used</div><div>for the simulations. As it was expected,</div><div>the initial rate method for the calorimetric</div><div>data, do not give a slope directly related</div><div>with the order of the reaction, as it</div><div>would be produced, for example, in data</div><div>from a spectrophotometer. However, a</div><div>linear relationship was found between</div><div>what we call the “calorimetric order”</div><div>and the kinetic order. Finally, the developed</div><div>procedure was applied to the study</div><div>of the H2O2 decomposition catalyzed</div><div>with Fe3+ in homogeneous phase and</div><div>with activated carbon in heterogeneous</div><div>phase, finding the order and the kinetics</div><div>constants of the global processes, which</div><div>were in close agreement with those in</div><div>the literature.</div>