3.1a. Application of Raoult's law to a binary system.
Repeat Example 3.1, but for a liquid concentration of 0.6 mole fraction of benzene and a temperature of 320 K.

Solution
3.2b. Application of Raoult's law to a binary system.
a) Determine the composition of the liquid in equilibrium with a vapor containing 60 mole percent benzene-40 mole percent toluene if the system exists in a vessel under 1 atm pressure. Predict the equilibrium temperature.

Solution
Initial estimates
b) Determine the composition of the vapor in equilibrium with a liquid containing 60 mole percent benzene-40 mole percent toluene if the system exists in a vessel under 1 atm pressure. Predict the equilibrium temperature.

Solution
3.3a. Application of Raoult's law to a binary system.
Normal heptane, n-C7H16, and normal octane, n-C8H18, form ideal solutions. At 373 K, normal heptane has a vapor pressure of 106 kPa and normal octane of 47.1 kPa.
a) What would be the composition of a heptane-octane solution that boils at 373 K under a 93 kPa pressure?

Solution
b) What would be the composition of the vapor in equilibrium with the solution that is described in (a)?

Solution
3.4a. Henry's law: saturation of water with oxygen.
A solution with oxygen dissolved in water containing 0.5 mg O2/100 g of H2O is brought in contact with a large volume of atmospheric air at 283 K and a total pressure of 1 atm. The Henry's law constant for the oxygen-water system at 283 K equals 3.27 ´ 104 atm/mole fraction.
a) Will the solution gain or lose oxygen?
b) What will be the concentration of oxygen in the final equilibrium solution?

Solution
At equilibrium:
Basis: 1 L water (1 kg water)
Equilibrium concentration, ce = 11.42 mg oxygen/L
Initial conditions:
The solution gains oxygen.
3.5c. Material balances combined with equilibrium relations.
Repeat Example 3.3, but assuming that the ammonia, air, and water are brought into contact in a closed container. There is 10 m3 of gas space over the liquid. Assuming that the gas-space volume and the temperature remain constant until equilibrium is achieved, modify the Mathcad program in Figure 3.2 to calculate:
a) the total pressure at equilibrium

Solution
Initial guesses
Answer: P = 1.755 atm
b) the equilibrium ammonia concentration in the gas and liquid phases.
Answer: yA = 0.145; xA= 0.162
3.6b. Mass-transfer resistances during absorption.
In the absorption of component A (molecular weight = 60) from an airstream into an aqueous solution, the bulk compositions of the two adjacent streams at a point in the apparatus were analyzed to be pA,G = 0.1 atm, and cA,L = 1.0 kmol of A/m3 of solution. The total pressure was 2.0 atm; the density of the solution was 1,100 kg/m3. The Henry's constant for these conditions was 0.85 atm/mole fraction. The overall gas coefficient was KG = 0.27 kmol/m2-hr-atm. If 57% of the total resistance to mass transfer resides in the gas film, determine

a) the gas-film coefficient, kG;

Solution
b) the liquid-film coefficient, kL;

Solution
Basis: 1 m3 of aqueous solution
c) the concentration on the liquid side of the interface, xA,i;

Solution
Initial estimates of interfacial concentrations:
d) the mass flux of A.

Solution
Check this result by calculating the gas-phase flux: