Chemical Engineering Thermodynamics  Phase Equilibrium
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 What is the significance of Van Laar constants? The vapor pressure of carbon tetra chloride  ethanol solutions are given below at 34.8^{o}C.
Weight percent CCl_{4} 
Vapor pressure, mm Hg 
0  100

10.23 
103 
20 
142 
27.13 
156 
39.06 
179 
43.87 
187 
48.86 
193 
58.25 
206 
71.68 
220 
76.69 
222 
84.25 
226 
92.98 
225 
97.43 
221 
98.46 
213 
100  203 
Calculate the Van Laar constants for this system at 34.8^{o}C.
 Using Van Laar method, compute the xy curve for ethanolwater mixtures at a total pressure of 760 mm Hg. Base the computations on the composition of the azeotrope 89.43 mole % alcohol at 78.15^{o}C. Vapor pressures at 78.15^{o}C: ethanol = 755 mm Hg; water = 329 mm Hg.
 From the following vapor pressure data, construct the temperature  composition diagram at 1 atm, for the system benzenetoluene, assuming ideal solution bahaviour.
Temperature ^{o}C 
Vapor pressure, mm Hg 
Benzene 
Toluene 
80 
760 
300 
92 
1078 
432 
100 
1344 
559 
110.4 
1748 
760 
 Construct Pxy diagram for the cyclohexane(1)  benzene(2) system at 40^{o}C. Use the following expressions for the liquidphase activity coefficients:
ln g
_{1} = 0.458 x_{2}^{2}
ln g
_{2} = 0.458 x_{1}^{2}
At 40^{o}C, P_{1}^{sat} = 0.243 atm; and P_{2}^{sat} = 0.241 atm.
 The vapor pressure of components A and B of a binary system at 80^{o}C and 760 mm Hg are 540 mm Hg and 620 mm Hg respectively. An azeotrope contains 20% A at 80^{o}C. Find Van Laar constants. What is the composition of a vapor corresponding to a liquid composition of 80% A?
 The azeotrope of propanolwater system has a composition of 43.2 mole % of propanol with a boiling point of 87.8^{o}C at a total pressure of 760 mm Hg. The vapor pressures of propanol and water at this temperature are 524 and 483 mm Hg respectively. Calculate the Van Laar constants and evaluate the activity coefficients of propanol and water for a solution containing 30 mole % propanol.
 The vapor pressure of toluene is given by the relation: ln P^{sat} = 13.9987  3096.52/(219.48 + t), where t is in ^{o}C and P^{sat} in kPa. What is the latent heat of vaporization at 107.2^{o}C?
 Two components A and B form a maximum boiling azeotrope at 90^{o}C and 760 mm Hg. The composition of azeotrope is 60 mole % A. The vapor pressure of A and B at 90^{o}C are 600 and 300 mm Hg respectively. Calculate the Margules constants and plot ln g
_{A }Vs. x_{A}.
 An experimental determination of a VLE state for ethanol  toluene system gave the following results. Vapor pressure at 45^{o}C: Ethanol = 173 mm Hg, Toluene = 75.4 mm Hg, x_{1} = 0.3 y_{1} = 0.634, P_{T} = 183 mm Hg. Calculate (i) the liquid phase activity coefficient (ii) does the liquid phase exhibit positive or negative deviation from ideal solution behavior?
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