UPSC CDS - Chemical Engineering Thermodynamics 1000+ MCQ [Solved] PDF Download

1. Clausius-Clapeyron Equation gives accurate result, when the
A. Vapour pressure is relatively low and the temperature does not vary over wide limits
B. Vapour obeys the ideal gas law and the latent heat of vaporisation is constant
C. Volume in the liquid state is negligible compared with that in the vapour state
D. All (A), (B) and (C)
Answer : D

2. A system is said to be at equilibrium, if the entropy of the system has reached __________ value.
A. Minimum
B. Zero
C. Maximum
D. None of these
Answer : C

3. Consider the process A & B shown in the figure given below: In this case, it is possible that

A. Both the processes are adiabatic
B. Both the processes are isothermal
C. Process A is isothermal while B is adiabatic
D. Process A is adiabatic while B is isothermal
Answer : C

4. The freezing point of a liquid decreases when the pressure is increased, if the liquid __________ while freezing.
A. Contracts
B. Expands
C. Does not change in volume
D. Either (A), (B) or (C)
Answer : A

5. All gases during throttling process at atmospheric temperature and pressure show a cooling effect except
A. CO₂
B. H₂
C. O₂
D. N₂
Answer : B

6. If atmospheric temperature and dew point are nearly equal, then the relative humidity is
A. Zero
B. 50%
C. Almost 100%
D. unpredictable
Answer : C

7. The Joule-Thomson co-efficient is defined as (?T/?P)_H. Its value at the inversion point is
A. ?
B. 1
C. 0
D. -ve
Answer : C

8. A gas shows deviation from ideal behaviour at
A. Low pressure and high temperature
B. Low pressure and low temperature
C. Low temperature and high pressure
D. High temperature and high pressure
Answer : C

9. Extensive properties of a thermodynamic system depend upon the __________ of the system.
A. Specific volume
B. Temperature
C. Mass
D. Pressure
Answer : C

10. The partial pressure of each constituent present in an alloy is __________ the total vapor pressure exerted by the alloy.
A. Less than
B. Equal to
C. More than
D. Either (B) or (C); depends on the type of alloy
Answer : A

11. Gibbs free energy at constant pressure and temperature under equilibrium conditions is
A. ?
B. 0
C. Maximum
D. Minimum
Answer : D

12. In the equation PVⁿ = constant, if the value of n = y = C_p/C_v, then it represents a reversible __________ process.
A. Isothermal
B. Adiabatic
C. Isentropic
D. Polytropic
Answer : C

13. Which of the following is not an intensive property?
A. Molar heat capacity
B. Internal energy
C. Viscosity
D. None of these
Answer : B

14. Entropy is a measure of the __________ of a system.
A. Disorder
B. Orderly behaviour
C. Temperature changes only
D. None of these
Answer : A

15. The work done in an adiabatic change in a particular gas depends upon changes in the __________ only.
A. Temperature
B. Specific heat
C. Volume
D. Pressure
Answer : A

16. The equilibrium constant for a chemical reaction at two different temperatures is given by
A. Kp₂/Kp₁ = - (?H/R) (1/T₂ - 1/T₁)
B. Kp₂/Kp₁ = (?H/R) (1/T₂ - 1/T₁)
C. Kp₂/Kp₁ = ?H (1/T₂ - 1/T₁)
D. Kp₂/Kp₁ = - (1/R) (1/T₂ - 1/T₁)
Answer : A

17. Which of the following is true for Virial equation of state?
A. Virial co-efficients are universal constants
B. Virial co-efficients 'B' represents three body interactions
C. Virial co-efficients are function of temperature only
D. For some gases, Virial equations and ideal gas equations are the same
Answer : C

18. Pick out the wrong statement.
A. A closed system does not permit exchange of mass with its surroundings but may permit exchange of energy.
B. An open system permits exchange of both mass and energy with its surroundings
C. The term microstate is used to characterise an individual, whereas macro-state is used to designate a group of micro-states with common characteristics
D. None of the above
Answer : D

19. Law of corresponding states says that
A. Two different gases behave similarly, if their reduced properties (i.e. P, V and T) are same
B. The surface of separation (i. e. the meniscus) between liquid and vapour phase disappears at the critical temperature
C. No gas can be liquefied above the critical temperature, howsoever high the pressure may be.
D. The molar heat of energy of gas at constant volume should be nearly constant (about 3 calories)
Answer : A

20. Melting of wax is accompanied with __________ in entropy.
A. Increase
B. Decrease
C. No change
D. None of these
Answer : A

21. The ammonia synthesis reaction represented by N₂ + 3H₂ ? 2NH₃; ?H = - 22.4 kcal, is
A. Endothermic
B. Exothermic
C. Isothermal
D. Adiabatic
Answer : B

22. An ideal liquid refrigerant should
A. Not have a sub-atmospheric vapour pressure at the temperature in the refrigerator coils
B. Not have unduly high vapour pressure at the condenser temperature
C. Both (A) and (B)
D. Have low specific heat
Answer : C

23. For multi-component multiple phases to be in equilibrium at the same pressure and temperature, the __________ of each component must be same in all phases.
A. Chemical potential
B. Fugacity
C. Both (A) and (B)
D. Neither (A) nor (B)
Answer : C

24. Gibbs free energy of a pure fluid approaches __________ as the pressure tends to zero at constant temperature.
A. Infinity
B. Minus infinity
C. Zero
D. None of these
Answer : B

25. Translational kinetic energy of molecules of an ideal gas is proportional to (where, T = absolute temperature of the gas)
A. T
B. ?T
C. T²
D. 1/?T
Answer : A

26. The extensive properties are
A. Volume, mass and number of moles
B. Free energy, entropy and enthalpy
C. Both (A) and (B)
D. None of these
Answer : C

27. The chemical potential for a pure substance is __________ its partial molal free energy.
A. More than
B. Less than
C. Equal to
D. Not related to
Answer : C

28. At equilibrium condition, the chemical potential of a material in different phases in contact with each other is equal. The chemical potential for a real gas (?) is given by (where, ? = standard chemical potential at unit fugacity (f° = 1 atm.) and the gas behaves ideally.)
A. ?° + RT ln f
B. ?°+ R ln f
C. ?° + T ln f
D. ?° + R/T ln f
Answer : A

29. If different processes are used to bring about the same chemical reaction, the enthalpy change is same for all of them. This is __________ law.
A. Hess's
B. Kirchoff's
C. Lavoisier and Laplace
D. None of these
Answer : A

30. The second law of thermodynamics states that
A. The energy change of a system undergoing any reversible process is zero
B. It is not possible to transfer heat from a lower temperature to a higher temperature
C. The total energy of system and surrounding remains the same
D. None of the above
Answer : D

31. An ideal gas is taken around the cycle ABCA as shown in P-V diagram below: The work done by the gas during the cycle is equal to

A. 12 P1V1
B. 6 P1 V1
C. 3 P1V1
D. P1 V1
Answer : C

32. A reasonably general expression for vapourliquid phase equilibrium at low to moderate pressure is ?_i y_i P = Y_i x_if_i° where, ? is a vapor fugacity component, Y_i is the liquid activity co-efficient and f_i° is the fugacity of the pure component i. the K_i value (Y_i = K_i x_i) is therefore, in general a function of
A. Temperature only
B. Temperature and pressure only
C. Temperature, pressure and liquid composition x_i only
D. Temperature, pressure, liquid composition x_i and vapour composition yi
Answer : C

33. The minimum number of phases that can exist in a system is
A. 0
B. 1
C. 2
D. 3
Answer : B

34. The equation, C_p - C_v = R, is true for __________ gas.
A. No
B. Any real
C. Only ideal
D. Both (B) and (C)
Answer : C

35. Measurement of thermodynamic property of temperature is facilitated by __________ law of thermodynamics.
A. 1st
B. Zeroth
C. 3rd
D. None of these
Answer : B

36. Which of the following exemplifies an adiabatic process?
A. Melting of ice
B. Condensation of alcohol vapor
C. Sudden bursting of a cycle tube
D. Evaporation of water
Answer : C

37. 1m3 of an ideal gas at 500 K and 1000 kPa expands reversibly to 5 times its initial volume in an insulated container. If the specific heat capacity (at constant pressure) of the gas is 21 J/mole . K, the final temperature will be
A. 35 K
B. 174 K
C. 274 K
D. 154 K
Answer : C

38. The quantitative effect of temperature on chemical equilibrium is given by the
A. Vant-Hoff equation
B. Le-Chatelier's principle
C. Arrhenius equation
D. None of these
Answer : A

39. The temperature at which both liquid and gas phases are identical, is called the __________ point.
A. Critical
B. Triple
C. Freezing
D. Boiling
Answer : A

41. Which of the following is not an intensive property?
A. Volume
B. Density
C. Temperature
D. Pressure
Answer : A

42. Specific/molar Gibbs free energy for a pure substance does not change during
A. Sublimation
B. Vaporisation
C. Melting
D. Either (A), (B) or (C)
Answer : D

43. Which of the following identities can be most easily used to verify steam table data for superheated steam?
A. (?T/?V)_S = (?p/?S)_V
B. (?T/?P)_S = (?V/?S)_P
C. (?P/?T)_V = (?S/?V)_T
D. (?V/?T)_P = -(?S/?P)_T
Answer : D

44. Fugacity and pressure are numerically equal, when the gas is
A. In standard state
B. At high pressure
C. At low temperature
D. In ideal state
Answer : D

45. An isentropic process is carried out at constant
A. Volume
B. Pressure
C. Temperature
D. All (A), (B) and (C)
Answer : A

46. Refrigeration capacity of a household refrigerator may be round about __________ tons.
A. 0.15
B. 1.5
C. 4.5
D. 6.5
Answer : A

47. Which of the following will increase the volume of a real gas by four times?
A. Doubling the absolute temperature as well as pressure of the gas
B. Reducing pressure to one fourth at constant temperature
C. Reducing temperature to one fourth at constant pressure
D. Reducing the temperature to half and doubling the pressure
Answer : B

48. Van Laar equation deals with the activity coefficients in
A. Binary solutions
B. Ternary solutions
C. Azeotropic mixture only
D. None of these
Answer : A

49. In the equation, PVⁿ = constant, if the value of n is in between 1 and y (i.e. C_p/C_v), then it represents a reversible __________ process.
A. Isometric
B. Polytropic
C. Isentropic
D. Isobaric
Answer : B

50. In which of the following reaction equilibrium, the value of equilibrium constant K_p will be more than is K_c?
A. 2HI ? H₂ + I₂
B. N₂O₄ ? 2NO₂
C. 2SO₂ + O₂ ? 2SO₃
D. None of these
Answer : B