METU, ChE 204
May 16, 2014
Thermodynamics I, Section 06
Prof. Dr. Tülay Özbelge
Asst. Emine Kayahan
HOMEWORK-10
(Date Due: May 23, 2014)
1. One hundred cubic meters of carbon dioxide initially at 150⁰C and 50 bar is to be
isothermally compressed in a frictionless piston-and-cylinder device to a final pressure of
300 bar. Calculate:
i. The volume of compressed gas
ii. The work done to compress the gas
iii. The heat flow on compression
iv. The change of enthalpy in the process
v. The change of entropy in the process.
Assuming carbon dioxide: (a) is an ideal gas, (b) obeys the principles of corresponding
states, Tc = 304.2 K, Pc = 73.76 bar
2. Ammonia is to be isothermally compressed in a specifically designed flow turbine from 1
bar and 100⁰C to 50 bar. If the compression is done reversibly, compute the heat and work
flows needed per mole of ammonia if
a. Ammonia obeys the principle of corresponding states
b. Ammonia satisfies the Clausius equation of state P(v – b) = RT with b = 3.730x10-2
m3/kmol.
3. A tank containing carbon dioxide at 400 K and 50 bar is vented until the temperature in the
tank falls to 300 K. Assuming there is no heat transfer between the gas and the tank, find
the pressure in the tank at the end of the venting process and the fraction of the initial mass
of gas remaining in the tank for each of the following cases.
a. The equation of state of carbon dioxide is P(v – b) = RT with b = 0.0441 m3/kmol.
b. Carbon dioxide obeys the law of corresponding states.
Note: The low-pressure (ideal gas) heat capacity of CO2 can be found in the Appendix.
4. One mole of n-butane in a piston – cylinder assembly undergoes an irreversible isothermal
expansion against a constant external pressure until the forces balance. The initial pressure
is 10 bar, and the initial molar volume is 3x10-3 m3/mol, and the final volume is 0.05
m3/mol. Take the temperature of the surroundings to be 298 K. Use the Van der Waals
equation of state and answer the following questions:
a.
b.
c.
d.
e.
What is the initial temperature?
What is the final pressure?
How much work is done during this process?
How much heat is transferred during this process?
What is the entropy change of the universe for this process
5. Ammonia is to be isothermally compressed during its flow through a compressor, from 1
bar and 100C to 50 bar. If the compression is done reversibly, compute the heat and work
flows needed per mole of ammonia if
(a) Ammonia obeys the Principle of Corresponding States,
(b) Ammonia satisfies the Clasius equation of state given by P(V-b) = RT where b = 3.73x102
m3/kmol.