physical chemistry i (tkk-2246) 14/15 semester 2 instructor: rama oktavian email:...
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Physical Chemistry I(TKK-2246)
14/15 Semester 2
Instructor: Rama OktavianEmail: [email protected] Hr.: M – F.13-15
Outlines
1. Review 1. Review
2. Liquid-liquid equilibria (2-components) 2. Liquid-liquid equilibria (2-components)
3. Liquid-liquid equilibria (3-components)3. Liquid-liquid equilibria (3-components)
4. Ternary diagrams 4. Ternary diagrams
Review
Review
Ch. 12Equilibrium 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. 12Phase diagram
Review
Ch. 12Phase rule
the phase rule for a one-component system
Gibbs Phase Rule
Review
Ch. 13Solution
Solution - homogeneous mixture of chemical species
One phase
Review
Ch. 13Raoult’s Law and Ideal Solution (only one volatile componet)
Raoult’s law
Review
Ch. 14Raoult’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
A + B
Liquid (bottom layer)
A + B
Liquid (upper layer)
1Ax
In equilibrium condition
2A
1A
21AA
Partially miscible solution
2Ax
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 arethe 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
735.041.0
41.083.0
l
l
n
n
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
0 1Xnicotine
Tem
pera
ture
( o C
)
X2X1 X3
T1
210 oC
61 oC
T2
T3
nicotine / water solution
nicotine saturated water rich phase in equilibrium with a water saturated nicotine rich phaseT4
lower consulate temperature
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 is in equilibrium with the predominant nicotine saturated water rich phase
As the system is further cooled there will be 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
mmHgp 4201
mmHgp 71802
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% A
100% B
Liquid-liquid equilibria
Ternary phase diagram
Ternary phase diagram for methyl isobutyl ketone + acetone + water
Liquid-liquid phase separation occurs
Binodal / cloud point curve
Plait point