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Set No. 1Code No: R05310803

III B.Tech I Semester Regular Examinations, November 2007

CHEMICAL ENGINEERING THERMODYNAMICS-II

(Chemical Engineering)

Time: 3 hours Max Marks: 80

Answer any FIVE Questions

All Questions carry equal marks

1. (a) The latent heat of vaporization of ethyl alcohol is experimentally to be 200

cal/gm. at its normal BP of 78 0C. Its critical temperature is 243 oC. Estimate

the heat of vaporization at a temperature of 180 oC.

(b) De ne of heat of solution based on one mole of solution and one mole of solute.

Also derive the relationship between them. [6+10]

2. The gas stream from a sulphur burner is composed of 45 mol % SO2, and 55 mol%

O2. This gas stream at 1 bar and 480 oC enters a catalytic converter when SO2

is further oxidized to SO3. Assuming that the reaction reaches equilibrium, deter-

mine how much heat must be removed from the converter to maintain isothermal

conditions per 100 mol of entering gas Cp / R = A + BT +D/T2 [16]

A 103 B 10-5 D Hf, 25oC Gof, 25oC

J/mol J/molSO2 5.699 0.801 -1.015 -296830 -300194

O2 3.639 0.506 -0.227 - - - - - - - - - -

SO3 8.060 1.056 -2.028 -395720 -371060

3. (a) Discuss the determination of fugacity from equation of state, with special

reference to Vander waals gas and show that, ln f = ln (RT/(V-b)) + b/(V-b)

? 2a/RTV.

(b) Show mathematically that the entropy change on mixing is not zero even for

ideal gases. [12+4]

4. (a) Elucidate the vapor-liquid equilibrium of binary systems with the help of p-x-yand t-x-y diagrams.

(b) Write and explain models for excess Gibbs energy based on the local compo-

sition. [12+4]

5. (a) Discuss the phase rule and Duhems theorem for non-reacting system, explain

in detail.

(b) The binary system of benzene (1) / ethyl benzene (2) conforms closely to

Raoults law. Vapor pressures for the pure species are given by the following

Antoine equations:

ln 1 sat = 13 8594 - 2773.78

t/0 C+220.07

ln 2 sat = 14 0045 - 3279.47t/0 C+213.2


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6. Determine expressions for GR, HR, SR implied by the vander waals equation of

state. [16]

7. Develop equations that apply to the limiting case of binary LLE for which the

-phase is very dilute in spices 1 and the -phase is very dilute in species2. [16]

8. A mixture of N2, H2 and Argon in the mole ratio 1:3:2 enters a catalytic reactor

for the synthesis of ammonia. The reactor is maintained at 400oC and 20 Mpa.

Estimate the degree of conversion (K = 1096*104). [16]


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1. If the heat capacity of the substance is correctly represented by in equation of the

form, p = + + 2

Show that the error resulting when p H is assumed = p evaluated at the

arithmetic mean of initial and nal temperature is ( 2 - 1)2 12. [16]

2. Calculate the maximum temperature in degree centigrade when the following gas

is burned with 30% excess air entering at 25 0 :

CO 30%

H2 15%

CO2 5%

N2 50%

The mean heat capacities of these gages (in cal/ g mole 0K) are:

CO : 7.587H2 : 7.138

O2 : 7.941

N2 : 7.507

CO2 :11.92

H2O : 9.39

Heat of combustion data: Hc (k cal/ g mole) CO = 67.63 and H2O = 68.32. [16]

3. Derive the relation for the calculation of Gibbs free energy of ideal gas mixture,

starting from fundamental property relation. [16]

4. Vapor-liquid equilibrium data for the system 1, 2 dichloro methane (1) /methanol

(2) at 50 oC are as follows:

P/kpa x1 y1

55.55 0.000 0.000

58.79 0.042 0.093

64.59 0.189 0.265

65.76 0.349 0.349

65.59 0.415 0.367

63.86 0.632 0.418

59.03 0.835 0.484

48.41 0.945 0.62031.10 1.000 1.000


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Determine the values of ln 1 and ln 2 using Margules equations. Also plot ln 1 and

ln 2 Vs x1. [16].

5. The excess Gibbs energy for a binary system is given by: GE / RT = 0.45 X1 X2.

The pure component vapor pressures are given by:

ln P1 sat kPa = 14 39- 2795.8

t/o C+230

ln P2 sat kPa = 16 59- 3644.2t/o C+239 [16]Obtain the P-x, y diagram for this system at 50oC.

6. Show that the residual Gibbs energy of uids from Redlich-Kwong equation of state

[16]is GR bRT 1 .5 ln (1 + ).RT = - 1 - ln(1 - ) - a

7. Name the di erent types of binary mixtures in terms of solubility. What are thethecritical solution temperature and the three phase temperature for a partially

miscible liquid solution. Show them on diagram. [16]

8. Write short notes on:

(a) E ect of temperature on equilibrium constant K

(b) Law of mass action.[8+8]


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1. Water and a liquid mixture of propane and butane are admitted into a vaporizer at

50 oC and leave as vapors at 175 oC. The hourly 25 kg water, 350 kg propane and

550 kg of butane are admitted. Estimate the heat requirement in the vaporizer.

Component Latent heat of vaporization Boiling point a b103 C106

cal/gm mole at 100o temp Tc o

Propane 5038 96.6 8.41 35.95 -6.97

Butane 6138 151.8 2.25 45.40 -8.83

Water 10388 96.6 7.14 2.64 0.046

Cp =a+bT+cT2 where Cp is in cal/mol.k and T is in K. Mention the assumption

made to solve the problem. [16]

2. Carbon monoxide gas is burned at constant pressure with 100% excess air. The

reactants enter at 25 0C and the exhaust gases leave the reaction chamber at 1200

0C Estimate the heat loss from the reaction chamberStandard heat of combustion of CO=-282,900 J/mol

Cp =a+bT+cT2 Cp in J/mol-K, T in K

The constants of a, b, c are:[16]

a b103 c106

CO2 26.75 42.26 -14.25

N2 27.02 5.81 -0.29

2 25.29 13.25 -4.20

3. (a) Derive an expression for estimating fugacity of a liquid at a given T and P.

(b) The partial molar volume of methanol in methanol- water. Solution at x1 =

0.3881 (mole fraction) is 39.176 10 -6 m3/mol. The density of the mixture

is 905.376 kg/m3. Calculate the partial molar volume of water in the solution.

[8+8]

4. Derive and discuss the Wilson equation as a model of solution behaviour for mul-

ticomponent system. Discuss the merits of this model over others. Explain its

temperature dependence also. [16]

5. (a) Explain bubble print and dewprint.

(b) Describe the vapor/ liquid equilibrium calculation procedure for DEW P. Va-por and liquid phases may be considered as non- ideal. [6+10]


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6. When the compressibility factor Z is a function of P, T show that the residual

dBdT . [16]entropy of uids from virial equation of state is SR R = -P R

7. Discuss about LLE and draw its solubility diagrams represented in the form of an

island [16]

8. In a laboratory investigation, acetylene is catalytically hydrogenated to ethylene at

1,1200C And 1 bar. If the feed is an equimolar mixture of acetylene and hydrogen,

what is the composition of the product stream at equilibrium? The reactions are

2 2 2 + 2 [16]K1= 4x105, K2 =2.5x10-6.2 + 2 2 2 4


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1. Water and a liquid mixture of propane and butane are admitted into a vaporizer at

50 oC and leave as vapors at 175 oC. The hourly 25 kg water, 350 kg propane and

550 kg of butane are admitted. Estimate the heat requirement in the vaporizer.

Component Latent heat of vaporization Boiling point a b103 C106

cal/gm mole at 100o temp Tc o

Propane 5038 96.6 8.41 35.95 -6.97

Butane 6138 151.8 2.25 45.40 -8.83

Water 10388 96.6 7.14 2.64 0.046

Cp =a+bT+cT2 where Cp is in cal/mol.k and T is in K. Mention the assumption

made to solve the problem. [16]

2. (a) 40 kg of ethyl alcohol and 50 kg of acetic acid are charged into a reactor to

yield ethyl acetate as per the reaction,

C2H5OH (l) + CH3COOH (l) = C2H5OOCCH3 + H2OThe reaction is 60% complete. Estimate the heat e ect of this process heat of

combustion in cal/mol: C2H5OH = -326700; CH3COOH = - 208300; C2H5OOCCH3

= - 538760, H2O( )= - 68.3 Kcal/gm mole.

(b) Write short notes on e ect of temperate on heat of reaction. [10+6]

3. (a) Estimate Z, HR and SR at 70 oC and 200Kpa for an equimolar vapor mixture

of propane and pentane using virial expansions B11 = -276, B22 = -809, B12

= -466 cm3/mol.

(b) Write and explain fundamental residual property relation. [10+6]

4. For Diethyl ether (1) - Chloroform (2) at 30 oC, a1 = 0.71 and a2 = 0.57, P1sat =sat = 86.59 kPa. The system is believed to governed by Margules

33.73 kPa and P2

type of equations for activity coe cients. Prepare a p-x-y diagram for the systemat 30 oC. [16]

5. (a) Explain bubble print and dewprint.

(b) Describe the vapor/ liquid equilibrium calculation procedure for DEW P. Va-

por and liquid phases may be considered as non- ideal. [6+10]

6. Show that the residual Gibbs energy of uids from Redlich-Kwong equation of state

[16]bRT 1 .5 ln (1 + ).is GRRT = - 1 - ln(1 - ) - a

7. Discuss about liquid-liquid Equilibrium (LLE). Draw liquid-liquid solubility dia-


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8. For the gas phase reaction CO2 (g) + 2H2 (g) CH3OH (g) at 10000 C and at

500 bar pressure,calculate the equilibrium composition using the following data:K = 0.68 at 10000C; The fugacity coe cients at this pressure:

CO2 =0.99; H2 = 1.15; CO = 1.08; H2O = 0.86. [16]

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