Thermodynamics help please!

i cannot get?number 2 on my homework and need some help please.

CHEG 2313

Thermo I HW#7

Spring 2016

Due Wednesday, April 6th at the beginning of class.
1. In class we worked through Illustration 4.5-1 in your book. Solve the problem again, this
time accounting for the temperature dependence of air (using App A-II). (6 pts)
2. 1 mol of Nitrogen (N2) enters a steady-state flow process at 800K and 50 bar and exits at
300K and 1 bar. Assume that the heat is transferred into this process at the exit
temperature. Determine the maximum work (J) that can be obtained.
Q
Nitrogen
T= 800K
P = 50 bar

T = 300K
P = 1 bar
W

a) Assume Nitrogen is an ideal gas with a constant Cp chosen from the following
published table: (6 pts)
Temperature
(K)
300
350
400
450
500
550
600
650
700
750
800

Specific Heat, Cp
(kJ/kgK)
1.040
1.041
1.044
1.049
1.056
1.065
1.075
1.086
1.098
1.110
1.122

b) Assume Nitrogen is an ideal gas with a Cp given in App A.II. (8 pts)
3. Calculate the entropy generated by the flow of 10 mol/s of nitrogen at 500oC and 500 bar

undergoing a Joule-Thomson expansion to 1 bar. For this case, assume nitrogen is an
ideal gas with a Cp*=3.923 kJ/kgK. (5 pts)