Rr310802 Chemical Engineering Thermodynamics II

Set No. 1

Code No: RR310802

III B.Tech I Semester Supplementary Examinations, February 2007 CHEMICAL ENGINEERING THERMODYNAMICS-II (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. If the heat capacity of a substance is correctly represented by an equation of the form, CP = A + BT + CT 2 Show that the error resulting when < Cp >H is assumed equal to CP evaluated at the arithmetic mean of the initial and final temperature is C(T2 − T1 )2 / 12. [16] 2. (a) Explain the Standard Heat of Combustion with suitable example. (b) Calculate the standard heat at 250 C for the following reaction, 4HCl(g) + O2 (g) → 2H2 O(g) + 2Cl(g) Standard heat of formation of HCl(g) = -92,307 J Standard heat of formation of H2 O(g) = -241,818 J (c) Given that the latent heat of vaporization of water at 1000 C is 2,257 J / gm. Estimate the latent heat at 3000 C. The critical temperature is 647.1 0 K Do not use steam table. [6+5+5] 3. (a) Define and explain partial property along with necessary equting. (b) The partial molar volume of ethanol in a 60% ethanol-water solution is 5.5x10−6 m3 . The density of the mixture is 849.4 kg/m3 . Calculate the partial molar volume of water in the mixture. [8+8] 4. (a) What is meant by data reduction? Explain how P − x − y data is reduced? (b) The excess Gibbs free energy of a binary liquid mixture at T and P is given E = ( 1.42x1 + 0.59x2 )x2 x1 . The vapour pressures are P1Sat = 82.37 by G RT Kpa, P2Sat = 37.31 Kpa. For given T and P, Using Margules equation find γ1 , γ2 and γ1α , γ2α . [8+8] 5. Explain bubble T calculations with neat flowchart along with relevant equations. [16] 6. For a mixture of 10mole % methane, zomole% ethane and 20 mole% propane at 500 F Determine the dew print pressure and the bubble point pressure. (Deprister chart should be provided during examination). [16] 7. Name the different types of binary mixtures in terms of solubility. What are the critical solution temperatures and the three phase temperature for a partially miscible liquid solution. Show them on diagram. [16] 8. Derive an equation from the fundamentals to describe the effect of temperature on ‘K’ in terms of ∆H 0 , ∆α ∆β ∆γ etc. Discuss the practical application of above derived equation with reference to any chemical reaction. [16] 1 of 2

Set No. 1

Code No: RR310802 ⋆⋆⋆⋆⋆

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Set No. 2

Code No: RR310802

III B.Tech I Semester Supplementary Examinations, February 2007 CHEMICAL ENGINEERING THERMODYNAMICS-II (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Calculate the heat required to raise the temperature of 1 mol of methane from 2600 C to 6000 C in steady flow process at a pressure sufficiently low that methane may be considered an ideal gas. Given the data, A = 1.702, B = 9.081x10−3 , and C = 2.164 x 10−6 (b) For steady flow in a heat exchanger at appropriate atmospheric pressure, what is the final temperature? i. When 10 mol of SO2 is heated from 200 to 1,1000 C? A=47.381, B=66× 10−3 ; C=1.1×10−9 . ii. When 12 mol of propane is heated from 250 to 1, 2000C? A= - 4.798, B=0.307, C= -0.16×10−3. [8+8] 2. Calculate the theoretical flame temperature of gas mixture consisting of 20% CO and 80% N2 when burned with 100% excess air, both air and gas initially being at 298K. The standard heat of reaction at 298K is -293.178 J/mol. The Heat capacity (J/mol.K) are given by Cp = a+bT +CT 2 . [16] CO2 O2 N2 ∧

a b∗103 c∗106 26.54 42.45 -14.298 25.61 13.26 -4.208 27.03 5.815 -0.289 ∧

3. Derive the expressions for φ1 and φ2 in a binary liquid mixture system.

[16]

4. (a) Show that the partial molar mass of a species in a solution is equal to its molar mass (molecular weight). (b) The excess Gibbs free energy of a binary liquid mixture at T and P is given E by G = ( -2.6 x1 -1.8x2 )x2 x1 . For the given T and P, find lnγ1 . and lnγ2 . RT (c) Define acitivity and activity coefficient.

[4+8+4]

5. (a) Discuss the Phase behavior for Vapor / Liquid systems. (b) Discuss about Retrograde Condensation.

[10+6]

6. Calculate the fraction of liquid, liquid composition and vapor composition in a two phase system consisting of acetone acetonitrile - nitromethane at 800 C and 110 Kpa. The overall composition of the mixture is Z=0.45, Z=0.35 and Z=0.2. The vapor pressures of the components (1), (2) and are 195.8 Kpa, 97.84 Kpa and 50.32 Kpa respectively. [16] 1 of 2

Set No. 2

Code No: RR310802

7. Show three types of constant pressure liquid-liquid solubility diagram with proper labeling. What do you mean by upper and lower consolute temperature. [16] 8. Derive an equation from the fundamentals to describe the effect of temperature on ‘K’ in terms of ∆H 0 , ∆α ∆β ∆γ etc. Discuss the practical application of above derived equation with reference to any chemical reaction. [16] ⋆⋆⋆⋆⋆

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Set No. 3

Code No: RR310802

III B.Tech I Semester Supplementary Examinations, February 2007 CHEMICAL ENGINEERING THERMODYNAMICS-II (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Calculate the heat required to raise the temperature of 1 mol of methane from 2600 C to 6000 C in steady flow process at a pressure sufficiently low that methane may be considered an ideal gas. Given the data, A = 1.702, B = 9.081x10−3 , and C = 2.164 x 10−6 (b) For steady flow in a heat exchanger at appropriate atmospheric pressure, what is the final temperature? i. When 10 mol of SO2 is heated from 200 to 1,1000 C? A=47.381, B=66× 10−3 ; C=1.1×10−9 . ii. When 12 mol of propane is heated from 250 to 1, 2000C? A= - 4.798, B=0.307, C= -0.16×10−3. [8+8] 2. Methane is burned with 20% excess air, both methane and air being at 298K. The standard heat of combustion of methane at 298K is (-802.625) kJ. The heat capacities (J/mol.K) are:Cp =a+bT+cT 2 . a b ∗103 c ∗106 Cp (CH4 ) 14.15 75.499 -17.9915 Cp (O2 ) 30.255 4.207 -1.8873 Cp (N2 ) 27.27 4.930 3.3256 Cp (CO2 ) 45.369 8.688 9.6193 Cp (H2 O) 28.850 12.055 1.006 Calculate the adiabatic flame temperature attained. [16] 3. (a) Define and explain partial property along with necessary equting. (b) The partial molar volume of ethanol in a 60% ethanol-water solution is 5.5x10−6 m3 . The density of the mixture is 849.4 kg/m3 . Calculate the partial molar volume of water in the mixture. [8+8] 4. (a) Show that the partial molar mass of a species in a solution is equal to its molar mass (molecular weight). (b) The excess Gibbs free energy of a binary liquid mixture at T and P is given E by G = ( -2.6 x1 -1.8x2 )x2 x1 . For the given T and P, find lnγ1 . and lnγ2 . RT (c) Define acitivity and activity coefficient.

[4+8+4]

5. (a) Characterize ideal solutions. (b) Two substances A and B are known to form ideal solution. An equimolar vapor mixture of A and B initially at 100 C and 100 Kpa is isothermally 1 of 2

Set No. 3

Code No: RR310802

compressed till the mixture condenses. Determine the pressures at which condensation begins and terminates and also the compositions of the vapor and liquid phases. The saturation pressures of A and B at 100 C are 120 Kpa and 150 Kpa, respectively. [6+10] 6. Determine expressions for G, H, S implied by the vander waals equations of state. [16] 7. Discuss thoroughly equilibrium and stability. Discuss by giving suitable example. [16] 8. Consider the reaction C4 H4 (g)→C4 H6 (g) + H2 (g). the standard free energy change is given by: ∆G0T = 24,760 − 5.01T ln T + 3.09T where ∆G0T is in J / mol butene and T is in K. (a) Over what range of temperature is the reaction promising from a thermodynamic viewpoint? (b) For reaction of pure butene at 800 K, calculate the equilibrium conversion for operation at 1 and 5 atm total pressure, assuming ideal gases. (c) Repeat part (b) at 1 atm for a feed of 50 mol % butene and 50 mol % inert gas and compare the results. [6+5+5] ⋆⋆⋆⋆⋆

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Set No. 4

Code No: RR310802

III B.Tech I Semester Supplementary Examinations, February 2007 CHEMICAL ENGINEERING THERMODYNAMICS-II (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) What are various empirical relations to calculate latent heat accompanying a phase change? (b) How can you calculate the latent heat of vaporization at some temperature from the knowledge of its value at a single temperature? (c) Write short notes on effect of temperature on heat capacity for gaves. [6+4+6] 2. Calculate the theoretical flame temperature of gas mixture consisting of 20% CO and 80% N2 when burned with 100% excess air, both air and gas initially being at 298K. The standard heat of reaction at 298K is -293.178 J/mol. The Heat capacity (J/mol.K) are given by Cp = a+bT +CT 2 . [16] CO2 O2 N2

a b∗103 c∗106 26.54 42.45 -14.298 25.61 13.26 -4.208 27.03 5.815 -0.289

3. (a) What is the property that is the contribution of a component as it exists in a solution and defines it mathematically? Give two examples. (b) It is required to prepare 3 m3 of a 60 mole percent ethanol − water mixture. Determine the volumes of ethanol and water to be mixed in order to prepare the required solution. The partial molar volumes of ethanol and water in 60 mole percent ethanol-water mixture are: V1 = 57.5 x 10−6 m3 /mol (ethanol); V2 = 16 x 10−6 m3 /mol; The molar volumes of the pure components are: Ethanol, v1 = 57.9x10−6 m3 /mol, Water, v2 = 18 x 10−6 m3 /mol. [8+8] 4. (a) What is meant by data reduction? Explain how P − x − y data is reduced? (b) The excess Gibbs free energy of a binary liquid mixture at T and P is given E by G = ( 1.42x1 + 0.59x2 )x2 x1 . The vapour pressures are P1Sat = 82.37 RT Kpa, P2Sat = 37.31 Kpa. For given T and P, Using Margules equation find γ1 , γ2 and γ1α , γ2α . [8+8] 5. (a) Discuss the Phase behavior for Vapor / Liquid systems. (b) Discuss about Retrograde Condensation.

[10+6]

6. Explain briefly the estimation procedure of thermodynamics properties from cubic equations of state along with equations. [16]

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Set No. 4

Code No: RR310802

7. Why does Immiscibility occur in liquid solution. How would you estimate the composition of the vapor phase in equation with two immiscible liquid phase?[16] 8. Calculate the dissociation pressure of Ag2 O at 2000 C use the following data: At 250 C, ∆H 0

=

28000 KJ/kg mole.

0

=

Ag2 O : CP

=

53.87 + 38.90 × 10−3 T

: CP

=

26.50 + 04.00 X 10−3 T.

For O2

∆G Ag : CP

8500 KJ/kg mole. = 20.60 + 06.50 × 10−3 T

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[16]