1.14d. Diffusivity of polar gases
If one or both components of a binary gas mixture are polar, a modified Lennard-Jones relation is often used. Brokaw (Ind. Eng. Chem. Process Design Develop., 8:240, 1969) has suggested an alternative method for this case. Equation (1-49) is still used, but the collision integral is now given by
mp = dipole moment, debyes [1 debye = 3.162 ´ 10-25 (J-m3)1/2]
a) Modify the Mathcad¨ routine of Figure 1.3 to implement Brokaw's method. Use the function name
DABp(T, P, MA, MB, mA, mB, VA, VB, TbA, TbB)
Solution

b) Estimate the diffusion coefficient for a mixture of methyl chloride and sulfur dioxide at 1 bar and 323 K, and compare it to the experimental value of 0.078 cm2/s. The data required to use Brokaw's relation are shown below (Reid, et al., 1987):

Parameter Methyl chloride Sulfur dioxide
Tb , K 249.1 263.2
Vb , cm3/mol 50.6 43.8
mp, debyes 1.9 1.6
M 50.5 64.06
Solution

1.15d. Diffusivity of polar gases
Evaluate the diffusion coefficient of hydrogen chloride in water at 373 K and 1 bar. The data required to use Brokaw's relation (see Problem 1.14) are shown below (Reid, et al., 1987):

Parameter Hydrogen chloride Water
Tb , K 188.1 373.2
Vb , cm3/mol 30.6 18.9
mp, debyes 1.1 1.8
M 36.5 18

Solution
1.16d. Diffusivity of polar gases
Evaluate the diffusion coefficient of hydrogen sulfide in sulfur dioxide at 298 K and 1.5 bar. The data required to use Brokaw's relation (seeProblem 1.14) are shown below (Reid, et al., 1987):

Parameter Hydrogen sulfide Sulfur dioxide
Tb , K 189.6 263.2
Vb , cm3/mol 35.03 43.8
mp, debyes 0.9 1.6
M 34.08 64.06

Solution