Physical Chemistry I (TKK-2246) 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) 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 Miscible – e.g: Toluene-benzene Partially miscible – e.g: water-phenol Immiscible – e.g: water-nitrobenzene

Liquid-liquid equilibria Basic concept Partially miscible solution In equilibrium condition Liquid (upper layer) A + B Liquid (bottom layer) A + B

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 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 1 Xnicotine Temperature ( oC ) X2 X1 X3 T1 210 oC 61 oC T2 T3 nicotine / water solution nicotine saturated water rich phase in equilibrium with a water saturated nicotine rich phase T4 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 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

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