Name: _____________________________ Score: ___________
LONG QUIZ 3
Thermodynamics
Test 1. Multiple choice:
_____ 1. What horsepower is required to isothermally compress 800 ft 3 of air per minute from
14.7 psia to 120 psia?
a. 28 hp c.256 hp
b. 108 hp d. 13,900 hp
_____ 2. A piston cylinder system contains a gas which expands under a constant pressure of
1200 lb/ft2. If the piston is displaced 12” during the process, and the piston diameter is 24”, what
is the work done by the gas on the piston?
a. 1768 ft-lbf c. 1890 ft-lbf
b. 2387 ft-lbf d. 3768 ft-lbf
_____ 3. Helium is compressed isothermally from 14.7 psia and 68F. The compression ratio is
4. Calculate the work done by the gas.
a. –1454 BTU/lb m c. –187 BTU/lbm
b. –364 BTU/ lbm d. 187 BTU/lbm
_____ 4. What is the change in entropy for no. 3?
a. –2.76 BTU/lbm-R c. 0
b. –0.689 d. 2.76.
_____ 5. The internal energy of a certain ideal gas is given by the expression u = 765 +
0.648pv ; Btu/lb where p is in psia. Determine the exponent k if this gas undergoes an isentropic
process.
a. 1.29 c. None of these
b. 1.423 d. 1.35
_____ 6. Helium undergoes a nonflow polytropic process from 300 liters and 410 kPaa to P 2 =
230 kPaa. If 148 kJ of work was added during the process, find n.
a. 1.559 c. 1.45
b. 1.65 d. None of these
_____ 7. For no. 6, find Q if cv for helium 3.1233 kJ/kg-K and k = 1.666
a. 32.445 kJ c. None of these
b. 243.157 kJ d. –45.153 kJ
_____ 8. Hydrogen at 2 lb/min undergoes a steady flow polytropic process from p1 = 50psia, V1=
90 ft3/lb and v1= 300 fps, until the pressure, volume and velocity are doubled. Determine
a. 2500 BTU c. –2500 BTU
b. 13170 BTU d. None of these
_____ 9. An Ideal gas contained in a rigid container undergoes a process that decreases the
internal energy by 316.5 kJ for 2.268 kg of a gas for which R = 430 J/Kg-K and k = 1.35. Find
the work.
a. –365.5 kJ c. 633 kJ
b. None of these d. 365.5 kJ
_____ 10. There are 1.36 kg of a gas for which R = 377 j/kg K and k = 1.25 that undergoes a
constant volume nonflow process from P1= 551.6 kPaa and t1 = 60 C to P2 = 1655 kPaa and
there are also added 105.5 kJ of heat. Determine t2.
a. 1129 K c. 1268 K
b. 999 K d. none of these
_____ 11. What is the change in entropy for no. 10?
a. 4.7512 kJ/K c. none of these
b. 2.253 kJ/K d. 0.4326 kJ/K
_____ 12. A mixture is formed at 684.48 kPaa, 37.8 C by bringing together theses gases
measured at the same pressure and temperature: 300 grams CO 2 , 200 grams N2 and 450 grams
of O2. Find the partial pressure of carbon dioxide.
a. 217.7 kPaa c. 193
b. 139.143 d. none of these
_____ 13. During the isentropic process of 4lb/sec of air, the temperature increases from 80F to
440F. Compute Q (cv = 0.1714 Btu/lb-R)
a. 987 BTU c. 345.6 BTU
b. 1332.6 BTU d. None of these
_____ 14. From no. 13, determine WSF if KE = -10Btu/s
a. –335.3 BTU/s c.355.3 BTU/s
b. 345.3 BTU/s d. None of these
_____ 15. What is the value of the work done for closed, reversible, isometric system?
a. Zero c. Negative
b. Positive d. Positive or negative
_____ 16. Calculate the change in enthalpy as 1 kg of nitrogen is heated from 1000 K to 1500 K,
assuming nitrogen is ideal and at constant pressure. The temperature dependent specific heat of
nitrogen is:
where cp is in kJ/Kmole-K and T is in K.
a. 600 kJ c.800.1 kJ
b. 700 kJ d. 649.72 kJ
_____ 17. 20 grams of oxygen are compressed isothermally at 30 C to 5% of the original
volume. What work is done on the system?
a. 824 cal c. 924 cal
b. 944 cal d. 1124 cal
_____ 18. Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is
heated and expands from 0.04 cu. m to 0.10 cu. m at a constant pressure of 200 kPaa. Calculate
the work done by the system.
a. 8 kJ c. 12 kJ
b. 10 kJ d. 16 kJ
_____ 19. The partial pressure of a four component gaseous mixture (CO, CH 4, N2, SO2) at 90F
are respectively 7, 21, 14 and 28 psia. What is the molecular weight of the mixture?
a. 29.98 c. 38.8
b. 32.14 d. None of these
_____ 20. In the PV diagram ahown, heat addition occurs between 1 and 2. Given that c v = 0.336
BTU/lbm-R, what is the entropy produced during this step?
2 461 psia, 2762 R
1 181 psia, 1081 R
a. –0.167 Btu/lbm-R c. 0
b. 0.234 d. 0.3150
Test 2. Fill in the blanks/ Identification
1. The Joule-Thomson experiment on ideal gases is commonly known as
________________________.
2. A constant enthalpy process is also known as __________________________.
3. All substances as they actually exist have _____________________________ according
to the third law of thermodynamics.
4. Joule and Thomson discovered from their experiment that for actual gases, h and u are
function of ___________________.
5. The total pressure of a mixture of gases is the sum of the pressures that each gas would
exert were it to occupy the vessel alone. This is known as _______________________.
6. Joule’s law states that the change in internal energy of an ideal gas is a function only of
_________________________.
7. The value of n for an isometric process is ___________.
8. For which type of process does the relation dQ = Tds hold? _____________________
9-10 State the 2rd law of thermodynamics.
