Physical Chemistry I (TKK-2246) 14/15 Semester 2 Instructor: Rama Oktavian Email:...

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


Basic concept

A + B

Liquid (bottom layer)

A + B

Liquid (upper layer)

1Ax

In equilibrium condition

2A

1A

21AA

Partially miscible solution

2Ax


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


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)


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



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




Critical solution temperature

1. The upper critical solution temperature, Tuc

2. The lower critical solution temperature, Tlc



1. The upper critical solution temperature, Tuc

The upper critical solution temperature, Tuc, is the highest temperature at which phase separation occur



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



Some systems have both Tuc and Tlc, with a famous example being

nicotine in water, where Tuc= 210oC and Tlc= 61oC


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)


Distillation of partially miscible liquids

First case - the Tuc is lower than the azeotrope temperature



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



Another case - the Tuc is higher than the azeotrope temperature



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).



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



Distillation of immiscible liquids

Immiscible liquids



Immiscible liquids

The total vapor pressures of liquids is





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


System of three components

Call Gibbs Phase Rule

P = 1, F = 4 – T, P, x1, x2

P = 2, F = 3 – T, P, x1


Ternary phase diagram

How to read it

100% C

100% A

100% B


Ternary phase diagram

Ternary phase diagram for methyl isobutyl ketone + acetone + water

Liquid-liquid phase separation occurs

Binodal / cloud point curve

Plait point

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Physical Chemistry I (TKK-2246) 14/15 Semester 2 Instructor: Rama Oktavian Email:...

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