Thermodynamics homework $15

1) [20 pts] The gas solubility of 1,1,1,3-tetrafluoroethane (R-134a) in the ionic liquid 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide ([HMIm][Tf2N] (the same system from HW#2) at 70°C is given to the right (Ren & Scurto, Fluid Phase Equil. 2009). As the ionic liquid has no measurable dew point, the vapor phase is considered pure. Determine the Henry’s Constant and the appropriate composition range (i.e. linear):

a) Assuming an ideal gas mixture vapor phase

b) Assuming the Peng-Robinson EoS is valid for R-134a

Note: to use the PR EoS program from the disk you need to add R-134a into the database that the software accesses for the properties. Go to the Microsoft Access database file (pure_prop.mdb) and insert the last row of the following (copy/paste) as a new compound at the end of the list. The folder and file should be in your “Program Files” folder.

(Technically only the Tc, Pc, and omega are needed for this HW)

2) [20 pts] 11.2-22

3) [40 pts] For the system Benzene (1) and CS2 (2), the 1-constant Margules expression adequately models the data due to the symmetry of activity coefficients. For data at a 50/50 mixture by mole, the GEX is equal to 290 J/mol at 25°C; and the HEX is = 525 J/mol (temperature independent). The melting point of benzene is 5.5°C (fusH=9.9 kJ/mol) and for CS2 is -108.6°C (fusH=4.39 kJ/mol).

a) [15 pts] Determine the Solid-Liquid Equilibrium across the composition/temperature range and plot

b) [15 pts] Determine if an upper consolute temperature (upper critical point) exists for this system. Be sure to show all stability requirements.

c) [10 pts] At 46.5°C, the vapor pressure of CS2 is 1.013 and for benzene 0.320 bar. Does a azeotrope form at this temperature?

4) [20 pts] 11.3-8: (use van Laar)

Optional Problems (not graded, but suggested):

1) 11.1-2 2) 11.2-9