Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Winter 5th Sem 2150503 Chemical Engineering Thermodynamics Ii Previous Question Paper
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER?V (NEW) EXAMINATION ? WINTER 2020
Subject Code: 2150503 Date: 03/02/2021
Subject Name: Chemical Engineering Thermodynamics - II
Time: 10:30 AM TO 12:30 PM Total Marks: 56
Instructions:
1. Attempt any FOUR questions out of EIGHT questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Discuss ideal and non-ideal solutions.
03
(b) For binary azeotrope mixture deviating positively form ideality, draw vapor-
04
liquid equilibrium (VLE) diagrams.
(c) Mixture of n-pentane (1) and n-heptane (2) conform to ideal solution behavior. 07
The vapour pressures of pure components are adequately described by Antoine
equations. Prepare P-x-y diagram at 70oC.
Use Antoine equation: log
sat
sat
10Pi
= Ai ? Bi /(t + Ci), where pressure Pi is in torr
and temperature t is in oC.
Component
A
B
C
n-pentane
6.8763
1075.78
233.2
n-heptane
6.8939
1264.37
216.64
Q.2 (a) With neat diagram, describe the effect of increasing pressure on binary T-x1-y1 03
vapour-liquid equilibrium (VLE) diagram.
(b) Write a short note on flash vaporization.
04
(c) Derive the equation for criteria for phase equilibrium in terms of chemical 07
potential for a mixture of N components and phases.
Q.3 (a) Write a brief note on retrograde condensation.
03
(b) The enthalpy at 300 K and 1 bar of a binary liquid mixture is represented by the
04
following equation:
H = 400 X1 + 600 X2 + X1 X2 (40X1 + 20X2), where H is in J/mol. Determine
expressions for H and H as functions of X
1
2
1.
(c) Define fugacity and fugacity coefficient. Discuss any two methods to evaluate 07
fugacity coefficient.
Q.4 (a) Discuss liquid-liquid equilibrium (LLE) in brief.
03
(b) Explain T-x-y diagram for partial miscible system.
04
(c) Write a short note on equilibrium and stability.
07
Q.5 (a) Write Raoult's law and Henry's law explaining each term associated with them 03
with their applicability.
(b) The ammonia synthesis reaction written as: 0.5 N2(g) + 1.5 H2(g) NH3(g) with 04
0.5 mol nitrogen and 1.5 mol hydrogen as the initial amounts of reactants and
with the assumption that the equilibrium mixture is an ideal gas, show that:
e = 1 ? (1 + 1.299KP) ?0.5
(c) For an ideal gas, the exact mathematical expressions can be developed for the 07
effect of T and P on the reaction co-ordinate at equilibrium. For conciseness we
let y iv K . Then we can write the mathematical relations:
i
1
K
d
K
d
e
y
and
e
y
e
T
T
dK
T
T
dK
P
P
y
T
T
y
Using above equations, show that
K
d
K d
e
0
i)
y
H
and ii)
e
y
e
(v)
2
T
RT dK
T
P dK
P
y
T
y
Q.6 (a) Write a short note on bubble point equilibria and dew-point equilibria.
03
(b) Explain Lewis-Randall Rule, and excess properties.
04
(c) Derive from the first principles, Go = - RT lnK.
07
Q.7 (a) Discuss the area test for checking the thermodynamic consistency of
03
experimental VLE data.
(b) Define partial molar properties. Discuss any one method to evaluate partial molar 04
properties.
(c) Water (1)/hydrazine (2) system forms an azeotrope containing 58.5 mol% 07
hydrazine at 393 K and 101.3 kPa. Calculate the equilibrium vapor composition
for a solution containing 20 mol% hydrazine. The relative volatility of water with
reference to hydrazine is 1.6 and may be assume to remain constant in the
temperature range involved. Vapor pressure of hydrazine at 393 K is 124.76 kPa.
Q.8 (a) Derive the Margules2 equations from the expression
=
211 + 122.
03
12
(b) Write a short note on group contribution methods.
04
(c) A liquid mixture of cyclohexanone (1)/ phenol (2) for which x1 = 0.6 is in 07
equilibrium with its vapour at 417.15 K. Determine the equilibrium pressure P
and vapour composition y1 from the following information:
2
2
ln = Ax and ln = Ax
1
2
2
1
At 417.15 K, p sat
sat
1
= 75.20 and p2 = 31.66 kPa
The system forms an azeotrope at 417.15 K for which x az
az
1 = y1 = 0.294.
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This post was last modified on 04 March 2021