Volume 3 is the third book of the volume series on physical Chemistry written by Dr. K L Kapoor. This book is useful for 2nd and 3rd semester students of B.Sc Chemistry (Hons and Gen). updated fifth edition on applications of Thermodynamics includes thoroughly updated chapter on electrochemical cells which has been written in accordance with the IUPAC recommendations. In addition to this, a brief discussion on the stability of ions of an element in different states of Oxidation has been added in terms of latimer and Frost diagrams. New illustrations on calculation of mean activity coefficient for an electrolyte have been added..