ITK-234
Termodinamika Teknik Kimia II
(2 SKS)
Dicky Dermawan
www.dickydermawan.net78.net
dickydermawan@gmail.com
Sylabus:
Multicomponent Thermodynamics
• Phase Equilibria
• Chemical Equilibria
(80%)
(20%)
Textbooks & References
• Smith, Introduction 2 Chemical
Engineering Thermodynamics
• Daubert, Chemical Engineering
Thermodynamics
Score & Grade
•
•
•
•
20
25
25
30
4
4
4
4
all homework & quiz
1st midterm exam
2nd midterm exam
final term examination
A 4 74.5 ++
B 4 59.5 ++
C 4 49.5 ++
D 4 39.5 ++
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
• Microsoft Excel
• MathCAD
Phase Equilibria Problem
Relation among
T, P, xi & yi at
equilibrium
condition
Experimental Approach
Mixture:
Methyl-ethyl-ketone (1) / Toluene (2)
Temperature:
50oC
P, kPa
15.51
18.61
21.63
24.01
25.92
27.96
29.96
30.12
31.75
34.15
x1
0.0895
0.1981
0.3193
0.4232
0.5119
0.6096
0.7135
0.7934
0.9102
y1
0.2716
0.4565
0.5934
0.6815
0.7440
0.8050
0.8639
0.9048
0.9590
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
T   T   ....  T 
P   P   ....  P 


 i   i  ....   i

i
The chemical potential of i-th
component is defined as:
  (nG) 
i  

 n i  T,P,n j
Criteria for Vapor - Liquid Equilibria
T T
g
P P
g


i g  i 
i
The chemical potential of i-th
component is defined as:
  (nG) 
i  

 n i  T,P,n j
Raoult’s Law
The chemical potential of i:
  (nG) 
i  

 n i  T,P,n j
For ideal gases:
i ig  G i ig  R  T  ln( yi )
For ideal solution:
i id  G i   R  T  ln( x i )
Neglecting effect of pressure on G i  , we obtain:
Raoult’s law
y i  P  x i  Pi
sat
Construction of Phase Diagram
Using Raoult’s Law: Binary Mixture
yi  P  x i  Pi sat
Physical Interpretation of Phase Diagram: Pxy
P - xy D ia gra m
A c e t o nit ril( 1) / N it ro m e t a na ( 2 ) @
75 o C
85
80
75
P
70
65
60
55
50
45
40
0
0.2
0.4
0.6
x1, y1
0.8
1
Physical Interpretation of Phase Diagram: txy
txy diagram
Acetonitril(1)/Nitrom ethane(2)
90
@ P = 70 kPa
t, oC
85
80
75
70
65
0
0.2
0.4 0.6
x1, y1
0.8
1
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:
3279,47
2788,51
sat
sat
ln
P
/
kPa

14
,
0045

ln P1 / kPa  13,8858 
2
o
t / o C  213,20
t / C  220,79
KUIS 1 HUKUM RAOULT
Kamis, 15 Maret 2007
2. Kesetimbangan uap - cair campuran biner n-pentana(1)/nheptana(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)
ln P1sat / kPa  13,8183 
2477,07
t / o C  233,21
ln P2sat / kPa  13,8587 
2911,32
t / o C  216,64