Consider the pentafluorethane [R-125] (1) + isobutane (2) system at 30°C. Using a gamma-phi modeling approach, calculate the Pxy diagram for the system using the 2-parameter Margules equation and the virial equation. Compare the predicted values with the experimental data provided in Table P12-18 (on the same plot). Also please provide two additional modeling approaches to the plot.

1. Model the system using modified Raoult’s Law (ideal gas for the vapor). This includes calculating the activity coefficients assuming an ideal gas for the vapor (as in Chapter 11). 

2. Model the system using Raoult’s Law.  

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TABLE P12-18 Vapor-liquid equilibrium of R-125 (1) + isobutane (2) at 30°C. P (MPa) 0.4070 0.6900 0.7376 0.8492 0.9714 1.0858 1.2240 1.3412 1.4530 1.5372 1.5652 1.5700 0 0.0816 0.0977 0.1492 0.2085 0.2889 0.4115 0.5371 0.6894 0.8510 0.9260 1 y₁ 0 0.3998 0.4474 0.5277 0.5977 0.6515 0.7125 0.7611 0.8200 0.8920 0.9384 1 Based on data from B-G Lee, et al., J. Chem. Eng. Data, 2000, 45, 760-763.