Lecture 4
     Systems of variable compositions & 
        Partial molar quantities.
       •  In Lecture 1
        The thermodynamic properties of fluids with constant composition was treated.
        
              But in chemical engineering we are faced with processes wherein the 
                                   composition of the fluids are varying.
                   •  For example,
                      – In chemical, petroleum or pharmaceuticals industries, 
                         multicomponent mixtures, gases or liquids undergo 
                         composition changes due to the following:
                      1. Mixing and separation processes
                      2. Transfer of species from one phase to another
                      3. Changes due to chemical reactions
                   •  Due to the fact that this type of system depend on 
                      composition as well as temperature and pressure, there 
                      is the need to develop a foundation theory for the 
                      application of thermodynamics to gaseous mixtures and 
                      liquid solution.
                  L2-04
                                        Department of Chemical/Petroleum Engineering, Afe Babalola University  © 2014
                  •  The theory is introduced via the derivation of fundamental 
                     property relation for homogenous solution of variable 
                     composition.
                  •  These derivations are based on a new property called 
                     Chemical Potential.
                  •  The chemical potential leads to the introduction of a new 
                     thermodynamic property called Partial Property . This is 
                     important in the treatment of real gas mixtures and form the 
                     basis for the introduction of Fugacity.
                 L2-05
                                       Department of Chemical/Petroleum Engineering, Afe Babalola University  © 2014
           Fundamental Property Relation
       Why is this fundamental property of importance 
           in solution thermodynamics?