Property Representation of 2-phase systems:
Consider a system consisting of liquid and vapor phases of a pure component coexisting in equilibrium. The total value of any extensive property of the two-phase system is the sum of the total properties of the phases. Let the total volume of the system be Vt; nL = mass (or moles) of liq, nV = mass (or moles of vapour.
Let Any Molar Thermodynamic Property
Thus, one may write: M = M L + xV M LV ...(2.34)
Where, M LV = M V– M L ...(2.35)
It may be noted that M is not a state variable, but an effective molar property of the system. The actual phase rule state variables are Mv and ML. The parameter xV – the mass fraction of vapour phase – in the system if called the ‘quality’.