Some Consequences of the Definition

It is convenient, therefore, to choose the pure condensed phase at the temperature of the solution at the equilibrium vapor pressure of the pure condensed phase as the standard state for the component in the solution (see Ref. 1). Thus, Equation (14.6) can also be written 

If Equation (14.2), Equation (14.6), or Equation (14.7) is used to define an ideal solution of two components, values for the changes in thermodynamic properties resulting from the formation of such a solution follow directly. 

No change in volume occurs when pure components that form an ideal solution are mixed. This statement can be validated for an ideal solution as follows. At any fixed 

Before the two pure components are mixed, the total volume Tinitiai is 

When the solution is formed, the total volume Vgnai is, from Equation (9.27), 

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