07 01 the Phase Rule

7/27/2019 07 01 the Phase Rule

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2010 Imam Siswanto

universitas airlangga

excellence with morality

KIMIA FISIKA IThe Phase Rule


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The Phase Rule

2010 Imam Siswanto Kimia Fisika I



The various type of heterogeneous equilibria : vaporation,sublimation, fusion, transition of one solid phase to another, solubility

of solids, liquids, etc.

A unified standpoint : phase rule.


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The Phase Rule




Definition

Three types of equilibrium :

1. True equilibrium : exist in a system when the same state can be

realized by approach from either direction.

2. Metastable equilibrium : can be realized by approach from either

direction.

3. Unstable equilibrium : system appears to undergo no change with

time.


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The Phase Rule




Definition

The number of component

: the smallest numberof independently variable constituents, in

term of whose formulas equations may be written expressing the

composition of each of the possible phases that may be occurs.

Example :

Water can be in three form : ice, liquid water and water vapor

Na2SO

4 water can be in : Na

2SO

4, Na

2SO

4.7H

2O, Na

2SO

4.10H

2O


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The Phase Rule




The degrees of freedom or the variance

: the smallest numberof independent variables (such as

pressure, temperature, concentration) that must be specified in

order to define completely the remaining variables of the system.

Example :

The density of water is 0.99973 gram per milliliter.

Definition


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The Phase Rule




The Gibbs Phase Rule

J. Willard Gibbs (1876) :

There is a definite relation in a system between the number of

degrees of freedom, the number of components, and the number of

phase present.

F = number of variablesnumber of equations

= [P(C-1) + 2][C(P-1)]

= CP + 2


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The Phase Rule




One-Component System

The complexity of one-component system depends on the number of

solid phases that can exist in the system.


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The Phase Rule




One-Component System

The System Water


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Two-Component System

When two components are present in a system, C = 2 andF = 4P.

If the temperature is constant, the remaining variance is F = 3 P,

which has the maximum value of 2.

One of these two remaining degrees of freedom is pressure andconcentration.


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The Phase Rule





Vapour pressure diagrams

Raoults law :

* *A A A B B Bp x p p x p

* * * * *( )A B A A B B B A B Ap p p x p x p p p p x


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The Phase Rule





The Composition of the vapour

The Daltons law for the gas :

A B

A B

p py y

p p

*

* * *

1

A AA

B A B A

B A

x py

p p p x

y y


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The Phase Rule





The Composition of the vapour

Relation between the total vapour pressure to the composition of the

vapour :

* *

* * *

A B

A B A A

p pp

p p p y


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The Phase Rule





The interpretation of the diagrams

Relation between the total vapour pressure to the composition of the

vapour :


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The Phase Rule





The interpretation of the diagrams


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The Phase Rule





The lever rule

n l n l


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The Phase Rule





Temperature-composition diagrams


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The Phase Rule





The distillation of mixtures

The efficiency of a fractionating column is

expressed in terms of the number of the

theoretical plates, the number of effective

vaporation and condensation and steps thatare required to archieve a condensate of given

composition from a given distillate.


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The Phase Rule





Azeotropes = boiling without changing


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The Phase Rule





Liquid-liquid phase diagrams, phase separation


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The Phase Rule





Critical Temperature

i it i l


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The Phase Rule





Critical Temperature

i it i l


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The Phase Rule





Liquid-solid phase diagrams

Th Ph R li it i l


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The Phase Rule

2010 I Si t Kimia Fisika I




Eutetics = easily melted

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07 01 the Phase Rule