Problem:

Calculate the enthalpy and entropy of saturated isobutene vapor at 360 K from the following information:1. compressibility-factor data for isobutene vapor.2. The vapor pressure of isobutane at 360 K is 15.41 bar.3. and for the ideal gas reference state at 300 K and 1 bar.4. The ideal-gas heat capacity of interest is:

Solution:

Compressibility Factors Z for Isobutane

P (bar)340 K350 K360 K370 K380 K

0.10.99770.997190.997370.997530.99767

0.50.987450.98830.989070.989770.9904

20.958950.962060.964830.96730.96953

40.924220.930690.936350.941320.94574

60.887420.898160.907340.915290.92223

80.845750.862180.875860.887450.89743

100.796590.821170.840770.856950.87061

120.77310.801030.823150.84134

140.755060.785310.80923

15.410.71727

Solving for in every pressure at 360 K:

P (bar) (bar-1)

0(0.031500)

0.10.026300

0.50.021860

20.017585

40.015913

60.015443

80.015518

100.015923

120.016581

140.017496

15.410.018347

*Value(s) in parenthesis are found by extrapolation

Plotting at each pressure:

At bar,

Graphing from 350 K to remove decreasing side:

At bar,

At bar,

At bar,

At bar,

At bar,

At bar,

At bar,

At bar,

Differentiating each trend line equation at and dividing each by corresponding pressure gives:

P (bar) (K-1bar-1)

0(1.757 x 10-4)

0.11.700 x 10-4

0.51.474 x 10-4

21.320 x 10-4

41.342 x 10-4

61.446 x 10-4

81.608 x 10-4

101.838 x 10-4

122.093 x 10-4

142.387 x 10-4

15.41(2.594 x 10-4)

*Value(s) in parenthesis are found by extrapolation

Plotting vs. : ,

Graphing : and

Abellar, Rodgie JohnAssignmentAries, Allen JerryChE Thermodynamics 2Belnas, Katrina LynJanuary 27,2014BSChE-4

20.0175850.03517

20.0160.032

20.01550.031

20.01550.031

20.0160.032

20.0165

20.01750.035

1.410.0183470.025869

Summary: