This book is the fifth of the six-volume series, which provides an extensive coverage of Physical Chemistry. Each volume includes a large number of illustrative numericals and typical problems to highlight the principles involved. IUPAC recommendations and SI units have been adopted throughout. The present book describes Adsorption, Chemical Kinetics, Photochemistry, Statistical Thermodynamics, and Macromolecules. A new chapter on Introduction to Irreversible Processes has been added.