Chemical Engineering Thermodynamics - 2 - Dec 2015

Chemical Engineering (Semester 5)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1(a) Write short note on Thermodynamic equilibrium(5 marks) 1(b) Write short notes on Gibbs Duhem Equation.(5 marks) 1(c) Explain Vandervaal's equation.(5 marks) 1(d) Explain properties of refrigerants.(5 marks) 2(a) For binary solution the activity coefficient of component is $$ \ln \gamma_1=Ax_2^2$$ where A is constant. x₂ is mole fraction of component 2. Obtain an expression for activity coefficient of component 2 in the same solution.(7 marks) 2(b) What azeotropic? What is the effect of pressure on the azeotropic composition?(6 marks) 2(c) Derive the relationship between the mole fraction of the components taking part in the reaction and the extent of the reaction.(7 marks) 3(a) Show that the fugacity of a gas obeying the vanderwaal's equation of state is given by: $$ \ln\ f=\dfrac{b}{v-b}-\dfrac{2a}{RTV}+ \ln\dfrac{RT}{V-b}$$(10 marks) 3(b) Describe the procedure to find the partial molar properties using the graphical method.(10 marks) 4(a) A gas mixture containing 25% CO, 55% H₂ and 20% inert gas is to be used for methanol synthesis. The gases issue from the catalyst chamber in chemical equilibrium with respect to the reaction: CO_(g)+2H_2(g)→CH₃OH_(g) at pressure of 300 bar and temperature of 625K. Assume that the equilibrium mixture forms an ideal solution and k_Ρ and k_Φ are 4.9 × 10^-3 and 0.35 respectively. What is the percent conversion of CO?(10 marks) 4(b) For a binary system of components A and B the activity coefficient are given by the relation lnγ₁=0.976x_B². The vapor phase data in bars are given by $$ \ln p_A^0=9.7321-\dfrac{2866.6}{t+217.88}; $$$$\ln p_A^0=12.0586-\dfrac{3667.7}{t+226.18}\ $$ is in °C. Does this system form an azeotropic at 71.7°C? If so at what composition?(10 marks) 5(a) A vapor compression refrigeration unit using Freon-12 operates between 151kpa and 746.6kpa. The fluid leaving the evaporator is saturated vapor and leaves the condenser at 303k. Calculate: (i) Refrigeration effect. (ii) Power required. (iii) COP. (iv) mass flow of refrigerant for refrigeration capacity of 4 Tons of refrigeration. Properties of Freon-12:
C_p=0.74 KJ/kgK

Attempt the following questions :

6(a) Explain vapor absorption refrigeration cycle with neat sketch(10 marks) 6(b) Explain various methods to determine thermodynamic critical properties with appropriate equations.(10 marks)