Chapter 3

Pagina 1

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 Chapter 3. Kinetic theory of Gases 3.1 Introduction The kinetic theory of gases, anticipated by intuitions of Newton, Herepath and Bernoulli, was developed and has been widely accepted by the scientific community in the second half of the 19th century thanks to two fundamental works published by Clausius in 1857 and by Maxwell in 1860. Subject and motivation of these studies was the attempt to describe the properties of a gas on the basis of the structural hypothesis that it is composed by a set of particles (atoms or molecules) that have a determined velocity and interaction energy. The results they wanted to achieve with this study were conceptually far-reaching. The aims of the study were to obtain a fundamental comprehension of what heat and temperature are, to find an explanation of the inverse proportionality between pressure and volume that was predicted by the ideal gas law, and to obtain a way to calculate the fundamental properties of gases, such as heat capacity, heat conductivity, viscosity and diffusion coefficient. The proposed path, extremely innovative at the time, was based on the hypothesis that the macroscopic properties of a thermodynamic system (like temperature and pressure) can be described from the comprehension of the characteristics of the elements that constitute such set, and thus from the study of its macroscopic properties. At the time these studies were considered with great…