Estudo de reações químicas homogêneas via método de Monte Carlo

Abstract

, having activation energy and temperature as parameters, it was possible to assess important dynamic aspects of homogeneous chemical reactions of the types A → B and A B. The protocol proved a useful tool in work with the basic concepts of Kinetics and Thermodynamics allowing its application both in class activities and for assisting experimental procedures.]]>

An Approach to the Kinetics and Thermodynamics of Elementary Chemical Reactions Using a Stochastic Model

“…Here the transition probability functions depend on the energy barrier (activation energy), temperature and steric factor. 11,12,19 Thus, when considering the elementary reaction between two species A ⇄ B, the transition probabilities, P f and P r , for the forward and reverse reactions are defined as follows (1) (2)…”

“…If a given box A i is occupied with a type-A molecule, the corresponding B i box will be empty and vice versa. In addition to the definition given in the literature, [10][11][12] the relationship between the total number of molecules is defined here as N ≡ N A + N B , and the total number of available boxes M is limited by N, such that N ≤ M. The effects of the number of molecules on the model can be investigated when N = N A + N B < M, for instance, by adding molecules during the simulation, with the case where N = M corresponding to the maximum capacity (full-filled case) of the containers (urns).…”

“…Since θ = k B T/E a , this behaviour can be interpreted in two different ways. 11,12 One is that the increase in θ means that the k B T term has to increase when using a constant activation energy. We thus explore the effect of temperature on a given system by defining a specific activation energy.…”

“…Teaching modules in chemical kinetics have used stochastic methods, such as the Monte Carlo method (MCM), to study chemical reactions. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] Stochastic methods offer a number of advantages. First, due to the lack of infrastructure at some school laboratories and universities, certain important topics in physical chemistry are either neglected or only treated theoretically.…”

“…Also, from a theoretical point of view, it is not always possible to analytically solve the system of ordinary differential equations that describe a chemical reaction due to its complexity. 12,13 A simple stochastic approach based on MCM and the Ehrenfest urn model (EUM) 12 is proposed here to overcome some of the difficulties associated with teaching chemistry by simulating the chemical kinetics of elementary reactions. This hybrid model takes into account the main kinetics parameters, such as temperature and activation energy, thus making it is possible to obtain features in chemical kinetics.…”