Extensive and molar properties of a thermodynamic system

The properties (state fimctions) which refer to the entire system and, therefore, are dependent on size (e.g. mass, volume) are termed extensive and may be represented by a generic quantity, Q. Those properties which are independent of the size of the system (e.g. temperature, pressure) are termed intensive. The ratio of any two extensive properties becomes an intensive property. A particularly useful quantity of this type arises when a particular Q is divided by the number of moles of material in 

The contrihution of each component to an extensive property of the system under isobaric and isothermal conditions is described by the 

The important Gibbs-Duhem relation between the partial molar quantities [5] is obtained by combination of the definition of Q in differential form, 

Similarly, the molar and partial molar quantities may be related and for the simple case of a binary system A-B with the mole fraction of 

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