Download GTU BE/B.Tech 2018 Winter 5th Sem New 2150503 Chemical Engineering Thermodynamics Ii Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY

BE - SEMESTER-V (NEW) EXAMINATION - WINTER 2018

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Subject Code:2150503 Date:16/11/2018

Subject Name: Chemical Engineering Thermodynamics-11

Time: 10:30 AM TO 01:00 PM Total Marks: 70

Instructions:

1. Attempt all questions.

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2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1

(a) For binary azeotropic mixture deviating positively from ideality, draw vapor-liquid equilibrium (VLE) diagrams. (03)

(b) Describe phase rule and Duhem’s theorem for non-reacting system. (04)

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(c) Define Lewis/Randall Rule. Derive Raoult’s law. What are the limitations of Raoult’s law? (07)

OR

Q.1

(a) With neat diagram describe the effect of increasing pressure on binary T-x1,y1 vapor-liquid equilibrium diagram. (03)

(b) Describe the phenomena of retrograde condensation. (04)

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(c) Assuming validity of Raoult’s law, draw P-xi,y1 diagram for binary mixture at 75 °C. Clearly show vapor region, liquid region, bubble point and dew point curves. (07)

Data given: At 75°C, P^sat₁=83.21kPa and P^sat₂=41.98 kPa

Q.2

(a) Define: (1) thermodynamic equilibrium, (2) chemical potential, and (3) fugacity coefficient for pure species i. (03)

(b) Describe graphical interpretation of following two equations relating partial molar properties with solution properties. (04)

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M_i=M+x_j (dM/dx_i) and M_j=M-x_i (dM/dx_i)

(c) Will it be possible to prepare 0.1 m³ of ethanol-water solution by mixing 0.03 m³ ethanol with 0.07 m³ pure water? If not possible, what volume should have been mixed in order to prepare a mixture of the same strength and of required volume? Density of ethanol and water are 789 and 997 kg/m³, respectively. The partial molar volumes of ethanol and water at the desired compositions are: Ethanol = 53.6 x 10^-6 m³/mol; water = 18 x 10^-6 m³/mol. (07)

OR

Q.2

(a) System acetone(1)/acetonitrile(2)/nitromethane(3) at 353.15 K has the overall composition z₁ = 0.45, z₂ = 0.35 and z₃ = 0.20. Assuming that the Raoult’s law is appropriate to this system, determine equilibrium pressure and vapor-liquid composition to carry out 40% vaporization. (07)

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Date Given: The vapor pressures of the pure species at the 353.15 K are: P^sat₁ = 195.75 kPa, P^sat₂ = 97.84 kPa and P^sat₃ = 50.32 kPa

Q.3

(a) For an ideal gas mixture, show that the ideal solution volume is equal to the sum of the pure component volumes, each measured at the mixture T and P. (03)

(b) For binary mixture derive following equations to calculate fugacity coefficient from virial equation of state. (04)

ln f_i = (B_ii + (2B_ij - B_ii - B_jj)x_j)P/RT

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(c) Derive an expression for the fugacity coefficient of a gas obeying the equation of state P(V-b)=R T and estimate the fugacity of ammonia at 10 bar and 298 K, given that b =3.707 x 10^-5 m³/mol. (07)

OR

Q.3

(a) Liquids A and B form an azeotrope containing 46.1 mole percent A at 101.3 kPa and 345 K. At 345 K, the vapor pressure of A is 84.8 kPa and that of B is 78.2 kPa. Calculate the van Laar constants. (07)

Q.4

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(b) Explain any one method for testing consistency of VLE data. (03)

(c) Describe Wilson and NRTL equations with their applications and limitations. (04)

OR

Q.4

(b) Describe Poynting correction. (03)

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(c) Discuss the effect of temperature, pressure and liquid phase composition on relative volatility of binary mixture following modified Raoult’s law. (04)

(a) The activity coefficients in a binary system are given by ln ?₁=Ax₂² and ln ?₂=Ax₁². Show that if the system forms an azeotrope, then azeotropic composition is given by X₁ = (1/2) - (ln(P^sat₂/P^sat₁))/(2A) (07)

Q.5

(b) Describe effect of temperature on reaction equilibrium constant. (03)

(c) Develop expressions for the mole fractions of reacting species as functions of the reaction coordinate for: (04)

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1. A system initially containing 2 mol NH₃ and 5 mol O₂ and undergoes the reaction: 4NH₃(g) +5O₂(g) = 4NO(g) +6H₂O(g)
2. A system initially containing 3 mol H₂S and 5 mol O₂ and undergoing the reaction: 2H₂S(g) +3O₂(g) = 2H₂O(g) +2SO₂(g)

(a) Explain block diagram for dew point pressure calculation. (07)

OR

Q.5

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(b) If G^E/RT = A x₁ x₂ for a liquid phase, show by stability analysis that LLE is predicted for A>2. (03)

(c) Briefly describe constant pressure liquid/liquid solubility diagrams. (04)

(a) Explain the method of Lagrange’s undetermined multipliers for gas phase reaction to minimize total Gibbs free energy. (07)

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