Thermodynamics 1

Thermodynamics-I http://unitoperation.com/Thermo/Thermo1.htm

Thermodynamics I

1. Which of the following equation is NOT TRUE for a mixture of solutes in a solvent?

_

Where, wi= weight fraction of the ith species
rI = density of the ith species
xi = mol fraction of the ith species

2. Mark the following variables as either Intensive property (A) or Extensive property (B)

(i) Composition A (ii) Pressure A (iii) Temperature A (iv) Total volume B
(v) Specific volume A (vi) Total enthalpy B (vii) molar entropy A

3. Mark the following systems as Open system (A) or Closed system (B) or Isolated system (C)

C (i) Water contained in a Dewar flask
B (ii) Water contained in aasealed containeratmosphere is being heated
is being heated
A (iii) Water contained in beaker open to

4. Match the following temperature scales as 0R (A) or 0F (B) or K (C) or 0C (D)

D C B A
5. Match the following values of R (Universal gas constant)

0.0821 (A) 10.73 (B) 1.987 (C) 0.7302 (D)

A B C D

6. Match the following as

Boyles’ law (A) Charle’s law (Isobaric) (B) Charles law (Isometric) (C) General law (D)

D (i) Pv/T = constant B (ii) vT = constant C (iii) PT = constant A (iv) Pv = constant

7. Match the following :

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Avagadro’s hypothesis (A) Gay Lussac’s law (B)
Gibbs-Dalton’s law (C) Graham’s law (D)

C (i) Total pressure of a mixture of gases that do not react with each other is equal to the partial pressures of each
of the constituent gases

B (ii) At a fixed temperature and pressure reacting gases combine with each other inn simple whole number of
proportions of volume

A (iii) Equal volume of gases at the same temperature and pressure contain the same number of gas molecules

D (iv) At the same temperature and pressure the rates of diffusion of gases are inversely proportional to the square
roots of their densities

8. STP (the Standard Temperature and Pressure) is

_
(a) 0°C and 1 atm. (b) 25°C and 1 atm. (c) 0 K and 1 atm.

9. For solids and liquid (far away from critical point) which of the following approximation are true.

(a) h u (b) CP Cv (c) _
(d) all of the above

10. For an ideal gas enthalpy
(a) Increases with pressure (b) Decreases with pressure.
_
(c) Independent of changes in pressure

11. Natural gas containing CH4 (77%), CO2 (4%), C2H6 (5%) and rest N2 is compressed to a pressure of 2 atm.
What is the partial pressure (atm) of CH4?

_
(a) 1.54 (b) 0.46 (c) 2.39

12. Natural gas is stored in a LPG bullet of 20m3 at a temperature of 400 K and 1.013 x 105 kPa. What is the
molar density of natural gas (assume ideal gas) ?

_
(a) 30.46 mol/m3 (b) 1.523 mol/m3 (c) 3.046 mol/m3

13. Instead of natural gas, air (also assume ideal) is stored at same bullet under identical conditions. What would
be the molar density of air? Average mol wt of natural gas = 19.50 kg/kmol and that of air = 28.8 kg/kmol.

_
(a) 30.46 m3 (b) 1.523 (c) 44.9 (d) 20.6

14. An adiabatic steady state turbine is the source for a small electric generator. Steam the motive fluid, enters at
600°C and 10 bar. Steam is exhausted from the turbine 1 atm pressure and 400°C. Estimate the work done by
turbine (kJ/kg steam) .

_
(a) –401.7 (b) 401.7 (c) –632.2 (d) 632.2

15. What is the amount of work done by a compressor (kJ/kmol) to compress an ideal gas isothermally at a
temperature of 25°C from 1 bar to 10 bars?

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(a) 5707.7 (b) 3293 (c) 57.07

16. An ideal gas at 35 bar and 600K leaks through a valve to an exit pressure of 7 bar. What would be the exit
temperature?

(a) 523.5K _
(b) 600K (c) 783.7K (d) None of these.

17. Nitrogen gas is stored in a 2 ft3 cylinder at a pressure of 3000 psia and temperature of 650F. What is the
molar density assuming nitrogen to be an ideal gas?

_
(a) 0.532 (b) 0.192 (c) 1.798

18. A cylinder (L1) containing LPG at 10 bars and 298 K is connected and is being used to fill another cylinder(L2
) initially at 1 bar and 298 K. The final temperature of L1 is T1 and that of L2 is T2. Then

(a) T1 > T2 (b) T1 = T2 _
(c) T1 < T2
_

19. What would be the entropy change (J/mol.K) due to the above filling process?

(a) 0 (b) 2.364 _
(c) 5.763 (d) None of these.

20i) is true for …

(a) For a reversible process only.
(b) For an irreversible process only.
_
(c) For both reversible and irreversible processes.

20ii). In a well-isolated bomb calorimeter nitrogen and hydrogen react to form ammonia. . Which of the following
is true?

_
(a) Total enthalpy remains constant.
(b) Total internal energy remains constant.
(c) Total entropy remains constant.

21. For an ideal gas specific internal energy is a function of

_
(a) temperature only
(b) temperature and pressure
(c) temperature, pressure and Gibbs free energy

22. The constant pressure heat capacity is defined as

_

23. The constant volume heat capacity is defined as

_

24. For an ideal gas the Cv and CP are functions of

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(a) temperature only (b) pressure only (c) both temperature and pressure

25. The values of CP and Cv for a monatomic gas are

_
(a) 5 and 3. (b) 3.987 and 1.987. (c) 0.66 and 1.987. (d) None of the above.

26. A well designed and insulated turbine can be assumed to operate at

(a) constant specific internal energy of the motive fluid
(b) constant specific enthalpy of the motive fluid
_
(c) constant specific entropy of the motive fluid
(d) constant temperature of the motive fluid

27. Two perfectly insulate tanks of equal volume are connected to each other. Initially tank 1 (L1) contains
LPG at 2 bar and 290 K and tank 2 (L2) is completely evacuated. The valve between the tanks is opened
and the pressures of the two tanks are allowed to equalize. Assuming LPG to be an ideal gas what is the
final temperature in tank L1 ?

(a) > 290 K _
(b) 290 K (c) > 290 K

28. A system consists of mixture of ice and water, amount of ice being 0.5 mol and water being 0.5 mol.
What is the sp. heat of the mixture ? (sp heat of water is 18 cal/mol.K and that of ice is 9 cal/mol.K )

(a) CP,mixture = 0 (b) CP,mixture = 18 (c) CP,mixture = 9 _
(d) CP,mixture = ∞

29. Which of the following plots is called Mollier diagram?

_
(a) h-s (b) h- P (c) T-s

30. In a Mollier diagram the slope of an isobar is given by

_
(c) 0 (d) ∞
31. An ideal gas, is compressed in a perfectly insulated compressor from 1 bar and T=25°C to a final pressure of
10 bar. What is the temperature of the gas exiting at 10 bars? g = 1.280

_
(a) 220°C (b) –92.8°C (c) –56.6°C

32. When water is vaporized to steam, the total amount of heat added is equal to …

(a) usteam – uwater _
(b) hsteam – hwater (c) ssteam – swater
(d) hsteam

33. The latent heat of vaporization of CO2 at -40°F and 145.8 psia is 137.8 Btu / lbm. The specific volume of
saturated vapor produced by vaporization is 0.6113 ft3/lbm. The enthalpy of saturated CO2 vapor at 145.8 psia is
137.8 Btu/lbm. What is its internal energy?

(a) 105.3 Btu/lbm. _
1(b) 21.3 Btu/lbm. (c) Need more data.

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34. For a process carried reversibly the rate of entropy generation within the system would be zero only when

(a) the process is isothermal
_
(b) the process is adiabatic
(c) for both isothermal and adiabatic process

35. The ratio of Cp/Cv for molecular nitrogen is

(a) 1.21 _
(b) 1.44 (c) 1.63 (d) none of the above.

36. For an ideal gas with Cp = 38 J/mol K, the value of g is

(a) 1.44 _
(b) 1.28 (c) 1.62 (d) None of the above.

37. When water is boiling in a beaker open to atmosphere, the latent heat of evaporation to be supplied is
equal to

(a) difference in specific internal energies of steam and water
_
(b) difference in specific enthalpies of steam and water
(c) difference in specific entropies of steam and water
(d) all of the above are true

38. An ideal gas with Cp = 30 kJ/kmol. K is heated in a double-pipe heat exchanger from 300K to 406 K at
a constant pressure of 1 bar. The amount of heat (kJ/kmol) to be added

(a) 5533 (b) 2299 _
(c) 3180 (d) None of the above.

39. For the above heat exchanger problem , the heat supplied to the gas is equal to the increase in

_
(a) Enthalpy (b) Internal energy (c) Neither ‘a’ nor ‘b’ (d) Need more data.

40. A compressor with a cooling jacket compresses air from 1 bar to 50 bar at a constant temperature of
406K. The difference in enthalpy (kJ/mol) between the inlet and outlet gas (CP = 30 J/mol.K) is

_
(a) 0 (b) 13.20 (c) Neither ‘a’ or ‘b’ (d) Problem not completely defined.
.
41. For the above compressor problem, the amount of heat (kJ/mol) removed by the cooling jacket is

(a) 0 _
(b) 13.20 (c) Neither ‘a’ or ‘b’. (d) Problem not completely defined.

42. In an insulated constant volume reactor, nitrogen and hydrogen combine to form ammonia at an
elevated temperature and pressure. Which of the following state variables remains constant during reaction?

(a) Enthalpy. _
(b) Internal energy. (c) Entropy. (d) None of the above.

43. Air is compressed adiabatically from 1 atm., 25°C to 10 atm. What is the exit temperature (0C ) of air
assuming it to be ideal (Cp = 38 J/mol.K)?

(a) 25 (b) 327 (c) – 25 _
(d) 220

44. Which of the following may be assumed as an isentropic process ?

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(a) steam flow in a smooth well designed converging nozzle
(b) heating of water by injecting of live steam through a diverging nozzle
(c) steam leaking through a partially opened valve
(d) mixing of sugar in water

45. In h-s diagram the dome shaped region is for

(a) vapor only (b) liquid only
_
(c) vapor-liquid mixture (d) super heated vapor.

46. For pure liquid methanol, how many state variables are required to completely define the system

(a) 1 _
(b) 2 (c) 3 (d) 4

47. Compressed air throttled through a needle valve to atmospheric pressure. The throttling process is

_
(a) Isenthalpic (b) Isentropic (c) Isobaric (d) Isothermal.

48. During a change of state, the change in which of the following state variable is equal to zero?

(a) specific enthalpy
(b) specific entropy
(c) specific internal energy
_
(d) molar Gibbs free energy

49. Melting of ice result in an
_
(a) Increases in entropy. (b) Decreases in entropy.
(c) Isentropic process. (d) None of these.

50. The triple point of most fluids is close to

(a) Boiling point
_
(b) Melting point. (c) Critical point.

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http://unitoperation.com/Thermo/MarksThermo1.html

Therodynamics I

Attempted:
Correct:
Percent:

1) (a) (b) (c)

2i) (a)

2ii) (a)

2iii) (a)

2iv) (a) (b)

2v) (a)

2vi) (b)

2vii) (a)

3i) (b) (c)

3ii) (a) (b)

3iii) (a)

4i) (a)
(d)
4ii) (a) (c)

4iii) (a) (b)

4iv) (a)

5i) (a)

5ii) (a) (b)

5iii) (b) (c)

5iv) (a)
(d)
6i) (a)
(d)
6ii) (a) (b)

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6iii) (a) (c)

6iv) (a)

7i) (a) (c)

7ii) (a) (b)

7iii) (a)

7iv) (a)
(d)
8) (a)

9) (a)
(d)
10) (a) (c)

11) (a)

12) (a)

13) (a)

14) (a) (b)

15) (a)

16) (a) (b)

17) (a) (b)

18) (a) (c)

19) (a) (c)

20i) (a) (c)

20ii) (a)

21) (a) (b)

22) (a) (b)

23) (a) (b)

24) (a)

25) (a) (b)

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26) (b) (c)

27) (a) (b)

28) (b)
(d)
29) (a) (b)

30) (a)

31) (a)

32) (b)

33) (a) (b)

34) (b)

35) (b)

36) (b)

37) (b)

38) (b) (c)

39) (a) (c)

40) (a)

41) (a) (b)

42) (b)

43) (b)
(d)
44) (a) (c)

45) (a) (c)

46) (a) (b)

47) (a) (b)

48) (a)
(d)
49) (a) (b)

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50) (a) (b)

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Thermodynamics 1

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