King Saud University- College of Engineering- Chemical Eng.
Che 501 Advanced Chemical Engineering Thermodynamics
Final Exams (3hrs)
Spring 1426/1427H 27-4-1427H
Q1 a) For a given data (x, y, P), explain the main steps required to determine the Margules two
parameter model for ∆G/RT.
b) Explain the methodology to calculate:
Bubl P (For a given T, and x) and dew P( for a given T, and y)
-c) Use the De Priester chart to determine the Dew P for a mixture of methane (0.15), propane
(0.4) and Ethane at 70F
Q2- a). It is required to separate a mixture of ethyl acetate and carbon tetrachloride usisng
distillation. The composition of vapour in contact with the liquid is required. At 25C the vapour
pressures of pure acetate and pure tetrachloride are, Pethyle acetate= 92mmHg and Pcarbon
tetra=111mmHg. Assuming the system obeys Raoult’s law, calculate the composition of liquid
and vapour phases that would be in equilibrium at P=100mmHg
B) The dissociation of isopropyl alcohol may be represented by the following reaction,
(CH3)2CHOHg = (CH3)2CO g + H2g
At 452K, and total P= 0.947atmos, the degree of dissociation using a suitable catalyst was found
0
to be 0.564. Determine the value of the equilibrium constant K, and hence G452
for the
dissociation reaction.( R=8.314j/gmole-K)
Q3.The process for production of ethanol is by the direct hydration of ethylene using phosphoric
acid catalyst. The temperature is around 600K.
C2H4(g) + H2O(g) = C2H5OH (g)
a) Use the Cp functions below to calculate Cp for the reactants
Cp(C2H5OH) = 19.9 +(20.95) 10-2 T – (10.37)10-5 T2 + (20.04) 10-9 T3
Cp(C2H4) = 3.5 +(15.63) 10-2 T – (8.339)10-5 T2 + (17.66) 10-9 T3
Cp(H2O) = 32.2 +(0.192) 10-2 T – (1.054)10-5 T2 + (3.594) 10-9 T3
o
b) Find ∆H for the reaction if H 298
(C2H5OH) = - 235.3 KJ/mol
o
H 298
(C2H4) = + 52.28 KJ/mol
c) Find
G
O
G298
O
298 (C2H4)g
for
the
o
H 298
(H2O) = - 241.8 KJ/mol
reaction
= +68.12KJ/mol G
d) Obtain a relationship for G
0
T
if
O
298 (H2O)g
O
G298
(C2H5OH)g
=
-168.6KJ/mol
= -227.6KJ/mol
in terms of constant and T terms
0
e) A company operating the process recommend T=572K, find G572
and K, the
equilibrium constant. Is this a small value, if so how is it the process can be worked
efficiently.
0
0
0
0
f) Calculate G572
from G572
= H 572
- T S 572
o
o
S 298
(C2H5OH)g = 160.7J/mol.K S 298
(C2H4)g = 219.5J/mol.K
T Cp
o
S 298
dT )
(H2O)g = 188.7J/mol.K ( S t0  
298 T
Compare this result with that from with (e), if the experimental measured Ka = (3.14)10-3.
g) If the initial parameters are: mole of ethylene =10, water vapour=6, T=572K, P=66.3atm,
calculate the moles of each component at initial point and at equilibrium (assume
x=moles ethanol formed at equilibrium), and finally the partilal pressures at equilibrium.
If the experimental Kp is used, determine the ethylene % conversion.