Download GTU B.Tech 2020 Winter 5th Sem 2150503 Chemical Engineering Thermodynamics Ii Question Paper

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Seat No.:

Subject Code: 2150503

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GUJARAT TECHNOLOGICAL UNIVERSITY

BE- SEMESTER-V (NEW) EXAMINATION — WINTER 2020

Subject Name: Chemical Engineering Thermodynamics - 11

Time: 10:30 AM TO 12:30 PM

Instructions:

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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

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(b) For binary azeotrope mixture deviating positively form ideality, draw vapor-liquid equilibrium (VLE) diagrams. 04

(c) Mixture of n-pentane (1) and n-heptane (2) conform to ideal solution behavior. The vapour pressures of pure components are adequately described by Antoine equations. Prepare P-x-y diagram at 70°C. 07

Use Antoine equation: log₁₀P_i^sat = A - B_i / (t + C_i), where pressure P_i^sat is in torr and temperature t is in °C.

Q.2

(a) With neat diagram, describe the effect of increasing pressure on binary T-x-y vapour-liquid equilibrium (VLE) diagram. 03

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(b) Write a short note on flash vaporization. 04

(c) Derive the equation for criteria for phase equilibrium in terms of chemical potential for a mixture of N components and p phases. 07

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 following equation: H = 400 X₁ + 600 X₂ + X₁ X₂ (40X₁ + 20X₂), where H is in J/mol. Determine expressions for H₁ and H₂ as functions of X₁. 04

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(c) Define fugacity and fugacity coefficient. Discuss any two methods to evaluate fugacity coefficient. 07

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

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Q.5

(a) Write Raoult’s law and Henry’s law explaining each term associated with them with their applicability. 03

(b) The ammonia synthesis reaction written as: 0.5 N_2(g) + 1.5 H_2(g) ? NH_3(g) with 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 + 1.299 K_p)^-1/2 04

(c) For an ideal gas, the exact mathematical expressions can be developed for the effect of T and P on the reaction co-ordinate at equilibrium. For conciseness we let H(T,P) = K. Then we can write the mathematical relations: 07

Date: 03/02/2021

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Total Marks: 56

Using above equations, show that

i) (?e/?P)_T = - (e/K) (?K/?P)_T and ii) (?e/?T)_P = - (e/K) (?K/?T)_P

Q.6

(a) Write a short note on bubble point equilibria and dew-point equilibria. 03

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(b) Explain Lewis-Randall Rule, and excess properties. 04

(c) Derive from the first principles, ?G^o = - RT lnK. 07

Q.7

(a) Discuss the area test for checking the thermodynamic consistency of experimental VLE data. 03

(b) Define partial molar properties. Discuss any one method to evaluate partial molar properties. 04

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(c) Water (1)/hydrazine (2) system forms an azeotrope containing 58.5 mol% 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. 07

Q.8

(a) Derive the Margules equations from the expression G^E/RT = A₂₁x₁x₂ + A₁₂x₁x₂. 03

(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 equilibrium with its vapour at 417.15 K. Determine the equilibrium pressure P and vapour composition y₁ from the following information: 07

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ln ?₁ = Ax₂² and ln ?₂ = Ax₁²

At 417.15 K, P₁^sat = 75.20 and P₂^sat = 31.66 kPa

The system forms an azeotrope at 417.15 K for which x₁^az = y₁^az = 0.294.