Chapter 1

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Notes of Applied Chemical Kinetics course Carlo Cavallotti Chapter 1. Introductory aspects and classification of chemical reactions Chapter 2. Kinetic schemes and reaction mechanisms Chapter 3. Kinetic theory of Gases Chapter 4. Fundamentals of Statistical Thermodynamics and Molecular Quantum Mechanics Chapter 5. Transition State Theory and further developments 2 3 Chapter 1. Introductory aspects and classification of chemical reactions 1.1 Introduction Chemical kinetics is the study of the chemical evolution of a reacting system in time. It assumes a complementary role with respect to thermodynamics, the scope of which is the study of equilibrium properties of a macroscopic system, independently from time and energy barriers that have to be overcome to reach the equilibrium. Notwithstanding this fundamental difference, chemical thermodynamics and kinetics are closely related, as will be shown during this course. For this reason, a good understanding of thermodynamics is needed to face the study of kinetics. From a historical point of view, chemical kinetics is a relatively young science, born in the second half of the XIX century with the works of Wilhelmy on the rate of inversion of sucrose, and with the study of Barthelot and Saint Gilles on the reaction between ethanol and acetic acid. It was in the beginning of the XX century that the studies on chemical kinetics acquired liveliness, benefiting from the developments of the kinetic theory of gases, and statistical thermodynamics, that provided the theoretical basis through which to interpret the experimental results. The field of study of kinetics pertains to all those systems in which a transformation occurs with a modification of the molecular composition of the chemical species involved, through the disruption…