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VAPOUR LIQUID

 EQUILIBRIUM

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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 phas !

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 "# Modifid Raoult’s Law

"i P = xi i Pisat ' i= 1,2,)..,*

Where

i = ctivit" coefficient.

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Eff*t of p(ssu( on VLE $h hi'h p(ssu(

dia'(ams a( a"o+ low p(ssu(,

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Equili"(ium Dia'(amVapo( *omposition is d(awn a'ainst liquid *omp at

*onstant p(ssu(, Vapou( is alwa#s (i*h in mo(+olatil *omponnt th *u(+ lis a"o+ th dia'onal

lin,

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Eff*t of +a(#in' p(ssu( on quili"(ium

dia'(am

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P%&%# Dia'(am

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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

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ctivit"'a*!3t is efine as the fuacit" of the existin conitionto the stanar state fuacit"

 a=f/ f o

ctivit" coefficient !3t measure the extent to %hich real solution epart from

iealit".

ln4=&x45

ln4=&x45

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Consistn*# tst fo( VLE data

  7sin slope of ln curves

  7sin ata at mi point

  #elich 8:ister metho

  7sin the coexistence euation

  7sin partial pressure ata

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Thank You