Chemical Engineering Thermodynamics - Phase Equilibrium

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1. What is the significance of Van Laar constants? The vapor pressure of carbon tetra chloride - ethanol solutions are given below at 34.8^oC.

Weight percent CCl4	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^oC.

2. Using Van Laar method, compute the x-y curve for ethanol-water 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^oC. Vapor pressures at 78.15^oC: ethanol = 755 mm Hg; water = 329 mm Hg.
3. From the following vapor pressure data, construct the temperature - composition diagram at 1 atm, for the system benzene-toluene, assuming ideal solution bahaviour.

Temperature oC	Vapor pressure, mm Hg
	Benzene	Toluene
80	760	300
92	1078	432
100	1344	559
110.4	1748	760

4. Construct Pxy diagram for the cyclohexane(1) - benzene(2) system at 40^oC. Use the following expressions for the liquid-phase activity coefficients:

ln g ₁ = 0.458 x₂²

ln g ₂ = 0.458 x₁²

At 40^oC, P₁^sat = 0.243 atm; and P₂^sat = 0.241 atm.

5. The vapor pressure of components A and B of a binary system at 80^oC and 760 mm Hg are 540 mm Hg and 620 mm Hg respectively. An azeotrope contains 20% A at 80^oC. Find Van Laar constants. What is the composition of a vapor corresponding to a liquid composition of 80% A?
6. The azeotrope of propanol-water system has a composition of 43.2 mole % of propanol with a boiling point of 87.8^oC 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.
7. The vapor pressure of toluene is given by the relation: ln P^sat = 13.9987 - 3096.52/(219.48 + t), where t is in ^oC and P^sat in kPa. What is the latent heat of vaporization at 107.2^oC?
8. Two components A and B form a maximum boiling azeotrope at 90^oC and 760 mm Hg. The composition of azeotrope is 60 mole % A. The vapor pressure of A and B at 90^oC are 600 and 300 mm Hg respectively. Calculate the Margules constants and plot ln g _A Vs. x_A.
9. An experimental determination of a VLE state for ethanol - toluene system gave the following results. Vapor pressure at 45^oC: Ethanol = 173 mm Hg, Toluene = 75.4 mm Hg, x₁ = 0.3 y₁ = 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?

Last Modified on: 04-Feb-2022

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