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[P T R Gupta]

Hi

Consider a point 'G' below bubble point curve on constant pressure equilibria curve of binary systems ( T vs x, y* curve). When we say 'G' represents entirely liquid solution, does that mean neither of the components are present in vapor state? Does it imply that vapor pressure of both the components at temperature corresponding to 'G' is zero? Please give me your views on the above.

 

Thanks

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[shantanuk100]

Hi PTR Gupta,

 

When you consider the vle curve, Let us take three points for easy illustration, and let Xi, Yi denote the X and Y values of pt. i on the graph.

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1. For Point G, the mixture is in completely liquid state with 

 

Mole fraction of A in liquid phase = Xg

Mole fraction of A in Vapor Phase = 0 (No point coincident with Vapor Region)

Mole fraction of B in liquid phase = 1-Xg = Yg

Mole fraction of B in Vapor phase = 0 (No point coincident with Vapor Region)

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2. For any intermediate point Q, on line LK,

 

there are two components A & B where each of the components have a certain amount of liquid fraction which is in equilibrium with that respective components vapor fraction.

 

Mole fraction of A in liquid phase = XL

Mole fraction of A in vapor phase = Xk

Overall Mole fraction of A in mixture = XQ

 

Mole fraction of B in liquid phase = (1-XL) = YL

Mole fraction of B in vapor phase = (1-Xk) = Yk

Overall Mole fraction of B in mixture = (1-XQ)

 

Overall mixture solid-vapor fractions are given by the Lever Rule

Fraction of A-B mixture in liquid phase = Length (KQ) / Length (LK)

Fraction of A-B mixture in vapor phase = Length (LQ) / Length (LK)

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3. For 3 it is similar to 1 except that now all points lie in vapor region and there is no coincident point with liquid section.

 

 

Regards,

Shantanu

Edited by shantanuk100, 20 April 2016 - 04:44 AM.