tailieunhanh - Ebook Physical chemistry (6/E): Part 2

(BQ) Part 2 book “Physical chemistry” has contents: Transport processes, reaction kinetics, quantum mechanics, atomic structure, molecular electronic structure, spectroscopy and photochemistry, statistical mechanics, and other contents. | 3/24/08 6:22 PM Page 474 CHAPTER 15 Transport Processes CHAPTER OUTLINE Kinetics Thermal Conductivity Viscosity Diffusion and Sedimentation Electrical Conductivity Electrical Conductivity of Electrolyte Solutions Summary KINETICS So far, we have discussed only equilibrium properties of systems. Processes in systems in equilibrium are reversible and are comparatively easy to treat. This chapter and the next deal with nonequilibrium processes, which are irreversible and hard to treat. The rate of a reversible process is infinitesimal. Irreversible processes occur at nonzero rates. The study of rate processes is called kinetics or dynamics. Kinetics is one of the four branches of physical chemistry (Fig. ). A system may be out of equilibrium because matter or energy or both are being transported between the system and its surroundings or between one part of the system and another. Such processes are transport processes, and the branch of kinetics that studies the rates and mechanisms of transport processes is physical kinetics. Even though neither matter nor energy is being transported through space, a system may be out of equilibrium because certain chemical species in the system are reacting to produce other species. The branch of kinetics that studies the rates and mechanisms of chemical reactions is chemical kinetics or reaction kinetics. Physical kinetics is discussed in Chapter 15 and chemical kinetics in Chapter 16. There are several kinds of transport processes. If temperature differences exist between the system and surroundings or within the system, it is not in thermal equilibrium and heat energy flows. Thermal conduction is studied in Sec. . If unbalanced forces exist in the system, it is not in mechanical equilibrium and parts of the system move. The flow of fluids is the subject of fluid dynamics (or fluid mechanics). Some aspects of fluid dynamics are treated in Sec. .