S.E. (Chemical) (Semester – II),University Of Pune Question Paper,2011 Question Paper,CHEMICAL ENGG. THERMODYNAMICS – I

University Of Pune Question Paper
S.E. (Chemical) (Semester – II) Examination, 2011
CHEMICAL ENGG. THERMODYNAMICS – I
(2003 Course)
Time : 3 Hours Max. Marks : 100
 Instructions : 1) Answer three questions from Section I and three questions
from Section II.
2) Answers to the two Sections should be written in separate
books.
3) Neat diagrams must be drawn wherever necessary.
4) Black figures to the right indicate full marks.
5) Use of logarithmic tables, slide rule, Mollier charts, electronic
pocket calculator and steam tables is allowed.
6) Assume suitable data, if necessary.
SECTION – I
1. a) State and explain first law of thermodynamics with its scope and limitations. 6
b) 1 kg of air is heated at constant pressure from an initial state of 300 K and 1 bar
untill its volume triples. Calculate W, Q, ΔH, ΔU for the process. Assume that
air obeys the relation PV/T = R = 83.14 cm3
/mol.k, Cp
 = 29 J/mol.k. 10
OR
2. a) Air at 1 bar and 298°C is compressed to 5 bar and 298 K by two mechanically
reversible processes.
a) Cooling at constant pressure followed by heating at constant volume.
b) Heating at constant volume followed by cooling at constant pressure
Calculate the heat and work requirements and ΔE and ΔH of the air for
each path. CV = 20.78 J/mol.k, CP = 29.10 J/mol.k for air PV/T = constant.
At 298 K and 1 bar the molar volume of air is 0.026 m3/mol. 16
3. a) Explain the P-T diagram for pure water showing clearly all the phase
regions. 8
b) State the importance of Van der Walls equation of state. Explain how this
equation was developed. 8
OR
[3962] – 339 -2-
4. a) Calculate the molar volume and compressibility factor for methanol vapor
at 500 k and 10 bar by using the following equations of state
i) Virial equation
ii) Redlich-Kwong equation
Virial coefficients are B = –2.19×104 m3/mol,
C = –1.73 × 10–8 m6/mol2,Tc = 512.6 k, Pc = 81 bar. Constants for
Radlich-Kwong equation
A = 21.7181 Nm4 k0.5/mol2, B = 4.5617 × 10–5 m3/mol. 10
b) Derive an equation for work done for the reversible adiabatic process. 6
5. Methanol is synthesized according to the following reaction.
CO(g) + 2H2
 (g) → CH3
OH (g)
The standard heats of formation at 298 K are – 110.125 KJ/mol for CO and –
200.660 KJ/mol for methanol. The specific heats (J/mol.k) are
CP
 (CH3
OH) = 19.382 + 101.564 × 10–3 T – 28.683 × 10–6 T2
CP (CO) = 28.068 + 4.631 × 10–3 T – 2.5773 × 10+4 T–2
CP
 (H2
) = 27.012 + 3.509 × 10–3 T + 6.9006 × 104
 T–2
a) Calculate the standard heat of reaction at 1073 K
b) Express the heat of reaction as a function of temperature. 18
OR
6. It is desired to carry out the following reaction at 600°C.
CO(g) + H2
O(g) → CO2
(g) + H2(g)
Estimate the standard enthalpy change of the reaction at 600°C if the standard
heat of reaction at 298 K is – 41.116 kJ. Use the following data :

CP= a + bT + cT2 + dT3
 + eT–2 J/mol.k
Compound a b × 103 e × 10–5
CO 28.068 4.631 – 0.258
H2
O 28.850 12.055 1.006
CO2 45.369 8.688 – 9.619
H2 27.012 3.509 0.690 18
-3- [3962] – 339
SECTION – II
7. a) Derive the following relation for the efficiency of carnot heat engine.
TH η = TH − TL 8
b) A nuclear power plant generates 750 MW, the reactor temp. is 588.15 k, and a
river with water temperature of 293.15 is available.
a) What is the maximum possible thermal efficiency of the plant, and what is
the minimum rate at which heat must be discarded to the river ?
b) If the actual thermal efficiency of the plant is 60% of the maximum, at what
rate heat must be discarded to the river, and what is the temperature
rise of the river if it has a flow rate of 165 m3/sec. 10
OR
8. a) Explain the concept of entropy. For irreversible thermodynamic process,
show that the total entropy change is positive. 8
b) Two compartments each of 1m3
 capacity are connected by a valve and
insulated from the surrounding and from each other. One compartment
contains saturated steam at 683.6 KPa and the other contains steam at the
same but at a pressure of 101.3 KPa. The valve is opened and the pressure
is allowed to equalize. Determine the change in entropy of the system
consisting of the two vessels. Comment on irreversibility of the process.
The thermodynamic properties of steam are as follows : 10
Pressure (KPa) H(KJ/kg) S(KJ/kgK)V(m3/kg) V(KJ/kg)
683.6 (T = 437.2 k) 2761 6.7133 278.9×10–3 2570.4
101.3 (T = 437.6 k) 2804 7.6712 1976.2 2603.3
9. a) Explain residual properties. Derive the fundamental residual property relation
for 1 mol of substance for closed thermodynamic system 8
( ) dT
RT
H dp RT
V
RT d G
2
R R R
= −
b) Derive the Clausius – Clapeyron equation for a two phase system. 8
OR
10. a) Show that
i) T P dV K dE CVdT ⎟
⎠
⎞ ⎜
⎝
⎛ − β = +
ii) dV
K
dT
T
CV dS β = + 10
b) Explain thermodynamic diagrams. 6
11. a) Explain absorption refrigeration cycle with neat sketch. 8
b) A vapor compression cycle using ammonia as refrigerant is employed in an
ice manufacturing plant. Cooling water at 288 k enters the condenser at a
rate of 0.25 kg/sec and leaves at 300 k. Ammonia at 294 k condenses at a rate
of 0.50 kg/min. Enthalpy of liquid ammonia at 294 k is 281.5 KJ/kg. The
compressor efficiency is 90%. Saturated ammonia vapor at 258 k and the
enthalpy of 1426 kJ/kg enters the compressor. What is the power
requirement of the compressor and refrigeration capacity in tons ? 8
OR
12 a) Explain Linde process for gas liquefaction. 6
b) A carnot engine is coupled to carnot refrigerator so that all the work produced
by the engine is produced by the engine is used by the refrigerator in extraction
of heat from a heat reservior at 0°C at the rate of 35 KW. The source of
energy for the carnot engine is a heat reservior at 250°C. If both devices
discard heat to the surrounding at 25°C how much heat does the engine
absorb from its heat source reservior ? If the actual coefficient of performance
of the refrigerator, COPactual = 0.60 COP carnot and if thermal efficiency of the
engine is ηactual = 0.60 ηcarnot, how much heat does the engine absorb from
its heat source reservoir ? 10
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