The relative volatility 12 is commonly used in applications involving binary VLE. In particular (see Ex.

The relative volatility α₁₂ is commonly used in applications involving binary VLE. In particular (see Ex. 13.1), it serves as a basis for assessing the possibility of binary azeotropy. (a) Develop an expression for α₁₂ based on Eqs. (13.13) and (13.14). (b) Specialize the expression to the composition limits x₁ = y₁ = 0 and x₁ = y₁ = 1. Compare with the result obtained from modified Raoult’s law, Eq. (13.19). The difference between the results reflects the effects of vapor-phase nonidealities. (c) Further specialize the results of part (b) to the case where the vapor phase is an ideal solution of real gases.

(Ex. 13.1)

For the system methanol(1)/methyl acetate(2), the following equations provide a reasonable correlation for the activity coefficients:

In addition, the following Antoine equations provide vapor pressures:

where T is in kelvins and the vapor pressures are in kPa. Assuming the validity of Eq. (13.19), calculate:

(a) P and { y_i} for T = 318.15 K and x₁ = 0.25.
(b) P and {x_i} for T = 318.15 K and y₁ = 0.60.
(c) T and { y_i} for P = 101.33 kPa and x₁ = 0.85.
(d) T and {x_i} for P = 101.33 kPa and y₁ = 0.40.
(e) The azeotropic pressure and the azeotropic composition for T = 318.15 K.

Eq. (13.19)

(a) Eq (13.13)

(a) Eq (13.14)

Transcribed Image Text:

In 71 = Ax} In 72 = Ax? where A = 2.771 - 0.00523T