14/15 Semester 2
Physical Chemistry I
(TKK-2246)
Instructor: Rama Oktavian
Email: rama.oktavian86@gmail.com
Office Hr.: M – F.13-15
Outlines
1. Review
2. Liquid-liquid equilibria (2-components)
3. Liquid-liquid equilibria (3-components)
4. Ternary diagrams
Review
Review
Ch. 12
Equilibrium condition
the chemical potential of each substance must have the same
value in every phase in which that substance appears
a state in which there are no observable changes as time goes by.
Review
Ch. 12
Phase diagram
Review
Ch. 12
Phase rule
the phase rule for a one-component system
Gibbs Phase Rule
Review
Ch. 13
Solution
Solution - homogeneous mixture of chemical species
One phase
Review
Ch. 13
Raoult’s Law and Ideal Solution (only one volatile componet)
Raoult’s law
Review
Ch. 14
Raoult’s Law and Binary Ideal Solution
Review
Ch. 14
Gaseous phase
Partial pressure of component 1
Review
Ch. 14
Review
Ch. 14
P-x,y diagram
Review
Ch. 14
T-x,y diagram
Review
Ch. 14
Azeotropes
Review
Ch. 14
Liquid-liquid equilibria
Basic concept of miscibility
1. Miscible – e.g: Toluene-benzene
2. Partially miscible – e.g: water-phenol
3. Immiscible – e.g: water-nitrobenzene
Liquid-liquid equilibria
Basic concept
Partially miscible solution
In equilibrium condition
Liquid (upper layer)
A+B
x A2
 A2
Liquid (bottom layer)
A+B
x1A
 1A
 
1
A
2
A
Liquid-liquid equilibria
Partially miscible liquid
P= 2, F= 1 the selection of temperature
makes the compositions of the
immiscible phases fixed
P= 1, F = 2 (two liquids are fully
mixed) both temperature and
composition can be changed
Liquid-liquid equilibria
Partially miscible liquid
1. Add small amount of nitrobenzene to
hexane at 290 K, it still dissolves
completely, P = 1
2. Add more nitrobenzene to hexane
and mixture of nitrobenzene-hexane
becomes saturated, add more
nitrobenzene, the mixture will
become two phases (line 2-3).
3. In point 3, the mixture will become
saturated (more nitrobenzene)
4. In point 4, the mixture will become
one phase (hexane will dissolve in
nitrobenzene)
Liquid-liquid equilibria
Representation of liquid liquid phase diagram
Point A - Mixture of 50 g hexane (0.59
mol C6H14) and 50 g nitrobenzene (0.41
mol C6H5NO2) was prepared at 290 K
A
There will be two phases solution with
the composition at point 2 and point 3
xN= 0.35 and xN= 0.83 (these are
the compositions of the two phases
Liquid-liquid equilibria
Representation of liquid liquid phase diagram
Use Lever-Rule to determine the ratio of
amount of each phase:
A
n l 0.83  0.41
 
7
n l 0.41  0.35
There is 7 times as much hexane-rich
phase as there nitrobenzene-rich
phase
If the mixture is heated to 292 K, we
go into a single phase region
Liquid-liquid equilibria
Representation of liquid liquid phase diagram
Liquid-liquid equilibria
Critical solution temperature
1. The upper critical solution temperature, Tuc
2. The lower critical solution temperature, Tlc
Liquid-liquid equilibria
Critical solution temperature
1. The upper critical solution temperature, Tuc
The upper critical solution temperature, Tuc, is the highest
temperature at which phase separation occur
Liquid-liquid equilibria
Critical solution temperature
2. The lower critical solution temperature, Tuc
The lower critical solution temperature, Tlc, is the lowest
temperature at which phase separation occur
For triethylamine and water, the
system is partially miscible above Tlc,
and single phase below
Liquid-liquid equilibria
Critical solution temperature
Some systems have both Tuc and Tlc, with a famous example being
nicotine in water, where Tuc= 210oC and Tlc= 61oC
Liquid-liquid equilibria
nicotine /
water solution
Temperature ( oC )
210 oC
T1
nicotine
saturated
water rich
phase in
equilibrium
with a water
saturated
nicotine rich
phase
T2
T3
T4
61 oC
0
X1 X2
Xnicotine
we cool a nicotine water solution of
composition X2 from some
temperature above the upper
consulate temperature of 210 oC.
At temperatures greater than T1 the
nicotine and water are miscible
When T1 is reached water saturated
nicotine rich phase just begins to form and
lower
consulate
is in equilibrium with the predominant
temperature
nicotine saturated water rich phase
As the system is further cooled there will be
X3
1 two phase region. In the two phase region the
relative amounts of the phases present are again
given by the lever law, e.g. at T2 we have:
nX1 (X2 - X1) = nX3 (X3 - X2)
Liquid-liquid equilibria
Distillation of partially miscible liquids
First case - the Tuc is lower than the azeotrope temperature
Liquid-liquid equilibria
Distillation of partially miscible liquids
a1 initial composition and temperature –
one phase
a2 the point where boiling begins and the
vapor will have composition at b1
When the distillate is cooled enough
to cause condensation, a single phase
first forms, represent by point b2
point b3 represents the overall
composition once the temperature is
lowered back to the starting
temperature
Liquid-liquid equilibria
Distillation of partially miscible liquids
Another case - the Tuc is higher than the azeotrope temperature
Liquid-liquid equilibria
Distillation of partially miscible liquids
a1 initial composition and temperature –
one phase
It will start boiling at point a2 with
vapor having composition given by
point b1
This distillate will condense into a two
phase liquid directly (b3).
Liquid-liquid equilibria
Distillation of partially miscible liquids
A system at e1 forms two phases up to the
boiling point at e2
condensing a vapor of composition e3
gives a two-phase liquid of the same
overall composition
At e2, F = 0, their compositions and
the temperature are fixed
Liquid-liquid equilibria
Liquid-liquid equilibria
Distillation of immiscible liquids
Immiscible liquids
Liquid-liquid equilibria
Distillation of immiscible liquids
Immiscible liquids
The total vapor pressures of liquids is
Liquid-liquid equilibria
Distillation of immiscible liquids
Liquid-liquid equilibria
Distillation of immiscible liquids
Example: Aniline(1)-water(2) system, we want to distill 100 g of
water from this mixture at 98.4°C under atmospheric condition
p10  42mmHg
p20  718mmHg
The mass of aniline that distills for each 100 g of water
Liquid-liquid equilibria
System of three components
Call Gibbs Phase Rule
P = 1, F = 4 – T, P, x1, x2
P = 2, F = 3 – T, P, x1
Liquid-liquid equilibria
Ternary phase diagram
How to read it
100% C
100% B
100% A
Liquid-liquid equilibria
Ternary phase diagram
Ternary phase diagram for methyl isobutyl ketone + acetone + water
Binodal / cloud point curve
Liquid-liquid phase
separation occurs
Plait point