# ITK-234 Termodinamika Teknik Kimia II

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ITK-234 Termodinamika Teknik Kimia II
(2 SKS) Dicky Dermawan

Sylabus: Multicomponent Thermodynamics
Phase Equilibria (80%) Chemical Equilibria (20%)

Textbooks & References
Smith, Introduction 2 Chemical Engineering Thermodynamics Daubert, Chemical Engineering Thermodynamics

Score & Grade 20 4 all homework & quiz 25 4 1st midterm exam
25 4 2nd midterm exam 30 4 final term examination A B C D

Phase Equilbria: Raoult’s Law

Nomenclature Closed System xi : mol fraction in liquid phase
yi : mol fraction in gas phase i = 1,2,3,… Sorted by vapor pressure from the higher one Vapor pressure: tendency of certain liquid to vaporize The higher the temperature, the higher the vapor pressure

Vapor Pressure Model Antoine P [=] torr t [=] oC

Antoine Vapor Pressure Model
P [=] torr t [=] oC

Antoine Vapor Pressure Model
P [=] torr t [=] oC

What will be needed in the near future: Hand Calculator Computer Programs

Phase Equilibria Problem
Relation among T, P, xi & yi at equilibrium condition

Experimental Approach
Mixture: Methyl-ethyl-ketone (1) / Toluene (2) Temperature: 50oC Plot the P-x-y diagram

Typical Diagram P-x-y diagram t-x-y diagram

Experimental Approach - Drawback
For the same binary mixture: Methyl-ethyl-ketone (1) / Toluene(2) What if we need the equilibrium data at 40oC? You’ve got to make experiment at that temperature! What if we need the equilibrium data at 60oC? You’ve got to make experiment at that temperature! What if we need the equilibrium data at 50oC? You already have one! Even for a simple binary mixture we must carry out many experiment in order to gather data

Experimental Approach - Drawback
What about other binary mixture: Chloroform (1) / Dioxane (2) You’ve got to perform other experiments! Diethyl ketone (1) / n-hexane (2) You’ve got to perform other experiments! Acetonitrile (1) / Nitromethane (2) You’ve got to perform other experiments! How many experiment should be carried out to obtain binary mixture vapor – liquid equilibria from a combination of 8 components? Waw!

Experimental Approach - Drawback
What about ternary mixture such as: Benzene (1) / Toluene (2) / Ethylbenzene (3) ? You’ve certainly got to perform other experiments! What about multicomponents mixture such as: Ethane (1) / Propane (2) / Isobutane (3) / Isopentane (4) ? You know the answer! How many experiment should be carried out to obtain mixtures vapor – liquid equilibria from a combination of 100 components? Waw!

Fundamental Question Do we really have to do these experiments?
100 years ago the answer is Yes! Not now! That’s why we take this course, folks!

Thermodynamics Approach: Criteria for System in Equilibria
The chemical potential of i-th component is defined as:

Criteria for Vapor - Liquid Equilibria
The chemical potential of i-th component is defined as:

Raoult’s Law The chemical potential of i: For ideal gases:
For ideal solution: Neglecting effect of pressure on , we obtain: Raoult’s law

Construction of Phase Diagram Using Raoult’s Law: Binary Mixture

Physical Interpretation of Phase Diagram: Pxy

Physical Interpretation of Phase Diagram: txy

Berdasarkan Diagram, Tentukan dan Tunjukkan:
a. Titik didih normal asetonitril b. Fasa campuran dengan fraksi mol asetonitril = 0,22 pada tekanan 70 kPa dan suhu 95oC c. Bila campuran ekimolar bersuhu kamar 25oC dipanaskan perlahan-lahan hingga mendidih, tentukan komposisi uap yang mula-mula terbentuk d. Pada temperatur berapa seluruh cairan pada (c) teruapkan ? e. Uap yang diperoleh pada (c) dikondensasikan. Cairan ini kemudian dibiarkan setimbang dengan uapnya pada tekanan 70 kPa. Gambarkan proses ini dalam diagram dan tentukan komposisi uap baru yang terbentuk.

Raoult’s Law: Binary Mixture

Raoult’s Law: Binary Mixture

Type of Phase Equilibria Calculations
Given T & P, find the equilibrium composition xi, yi BUBL P calculation: Given T & liquid composition xi, Find the bubble point Pb & vapor composition DEW P calculation: Given T & vapor composition yi, Find the dew point Pd & vapor composition

Type of Phase Equilibria Calculations
BUBL t calculation: Given P & liquid composition xi, Find the bubble point tb & vapor composition DEW t calculation: Given P & vapor composition yi, Find the dew point Pd & vapor composition FLASH calculation: Given P, T & overall composition, Find the fraction of system which is liquid (L) & vapor (V) and their respective compositions xi & yi

Raoult’s Law; Binary Mixture

Type of Phase Equilibria Calculations
a. Given T= 100oC & P = 1 atm, find the equilibrium composition xi, yi b. BUBL P calculation: Given T = 100oC & liquid composition x1 = 25% Find the bubble point Pb & vapor composition c. DEW P calculation: Given T = 100oC & vapor composition y1 = 25%, Find the dew point Pd & dew composition

Type of Phase Equilibria Calculations
d. BUBL t calculation: Given P = 1 atm & liquid composition x1= 25% Find the bubble point tb & vapor composition e. DEW t calculation: Given P = 1 atm & vapor composition y1,= 25% Find the dew point td & dew composition f. FLASH calculation: Given P = 1 atm, T = 115oC & overall composition, z1=25% Find the fraction of system which is liquid (L) & vapor (V) and their respective compositions xi & yi

Do we always have to prepare phase diagram to make calculation?
No, we don’t have to We can just perform the calculations

Raoult’s Law: Binary mixture

Raoult’s Law: Binary mixture

Extension to Ternary and Multi Component Mixtures
We can’t even prepare the diagram! But we still able to make the calculations

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

Raoult’s Law: Ternary Mixture

KUIS 1 HUKUM RAOULT Kamis, 15 Maret 2007
1. Dengan asumsi keberlakuan Hukum Raoult, sketsalah diagram txy untuk campuran biner benzena(1)/etilbenzena(2) pada tekanan 101,33 kPa. Berdasarkan diagram yang saudara konstruksi, tentukan dan tunjukkan dalam diagram: a. Titik didih normal etilbenzena b. Fasa campuran dengan fraksi mol etilbenzena = 0,22 pada tekanan atmosferik dan suhu 110oC c. Bila campuran ekimolar bersuhu kamar 25oC dipanaskan perlahan-lahan hingga mendidih, tentukan komposisi uap yang mula-mula terbentuk d. Pada temperatur berapa seluruh cairan pada (c) teruapkan ? e. Uap yang diperoleh pada (c) dikondensasikan sehingga mencair. Cairan ini kemudian dibiarkan setimbang dengan uapnya pada tekanan atmosferik. Gambarkan proses ini dalam diagram dan tentukan komposisi uap baru yang terbentuk. Tekanan uap masing-masing komponen murni mengikuti persamaan:

KUIS 1 HUKUM RAOULT Kamis, 15 Maret 2007
2. Kesetimbangan uap - cair campuran biner n-pentana(1)/n-heptana(2), karena kemiripan struktur molekulnya, dapat diasumsikan memenuhi hukum Raoult. Pada tekanan konstan 115 kPa: a. Tunjukkan bahwa campuran dengan komposisi 60% mol n-pentana pada suhu 100oC berfasa uap b. Campuran pada (a) didinginkan perlahan-lahan hingga uap mengembun sedikit demi sedikit. Perkirakan suhu yang diperlukan untuk mengembunkan 50% dari uap pada (a)

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