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  At equilibrium no driving force for energyor mass transfer .

  Equilibrium is the static condition inwhich no change occur in themacroscopic properties of a system withtime

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Dalton’s law

Ptotal = p1+ p2Where,

Ptotal  -Total pressure p1 ,p2 -Partial pressure of component.

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Composition of liquid phase :

x1= p1/ p10

  =  partial pressure of component /vapour pressure of pure component

Composition in aseous phase !" 1= p1/ P

  =  partial pressure of component /total pressure#aoult$s la% &ecomes

"iP=xiPisat  'i=1,2,()..n*

Where!

"i = apor-phase mole fraction.xi = iui-phase mole fraction.

Pi = apor pressure of pure species i at the T of the s"stem.

"i P = Partial pressure of species i.

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VLE by Modified Raoult’s Law

"i P = xi i Pisat ' i= 1,2,)..,*

Where

i = ctivit" coefficient.

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Effect of pressure on VLE The hih pressure

diarams are abo!e low pressure"

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Equilibrium DiaramVapor composition is drawn aainst liquid comp at

constant pressure" Vapour is always rich in more!olatile component the cur!e lies abo!e the diaonal

line"

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Effect of !aryin pressure on equilibrium

diaram

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#$%$y Diaram

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uacit"! 3t is erive from atin, expresse as

fleetness or escapin tenenc". 3t is useto stu" extensivel" phase an chemical reaction

euili&rium.

G = RT ln f +ɵ

 - Is an constant depends on temperature and natureɵ

of gas.

fuacit" has same units as pressure for an ieal as.

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uacit" coefficient '  ) :ɸ uacit" coefficient is efine as the ratio of fuacit"

of component to its pressure.

=f/P ɸ

- 3s the measure of non ieal &ehavior of the as.ɸ