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

1. Absorption/evolution of heat during conversion of a substance from one allotropic form to another is termed as the heat of
A. Sublimation
B. Fusion
C. Transition
D. Vaporisation
Answer : C

2. Pick out the correct statement.
A. Like internal energy and enthalpy, the absolute value of standard entropy for elementary substances is zero
B. Melting of ice involves increase in enthalpy and a decrease in randomness
C. The internal energy of an ideal gas depends only on its pressure
D. Maximum work is done under reversible conditions
Answer : D

3. Which of the following is Virial equation of state?
A. (p + a/V²)(V - b) = nRT
B. PV = nRT
C. PV = A + B/V + C/V² + D/V³ + ...
D. None of these
Answer : C

4. Free energy change of mixing two liquid substances is a function of the
A. Concentration of the constituents only
B. Quantities of the constituents only
C. Temperature only
D. All (A), (B) and (C)
Answer : D

5. The free energy change for a chemical reaction is given by (where, K = equilibrium constant)
A. RT ln K
B. -RT ln K
C. -R ln K
D. T ln K
Answer : B

6. When a gas in a vessel expands, its internal energy decreases. The process involved is
A. Reversible
B. Irreversible
C. Isothermal
D. Adiabatic
Answer : A

7. Which of the following units is not present in both the vapor compression refrigeration system and absorption refrigeration system?
A. Expansion valve
B. Condenser
C. Refrigerator
D. Compressor
Answer : D

8. A cylinder contains 640 gm of liquid oxygen. The volume occupied (in litres) by the oxygen, when it is released and brought to standard conditions (0°C, 760 mm Hg) will be __________ litres.
A. 448
B. 224
C. 22.4
D. Data insufficient; can't be computed
Answer : A

9. 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

10. The equation, PV = nRT, is best obeyed by gases at
A. Low pressure & high temperature
B. High pressure & low temperature
C. Low pressure & low temperature
D. None of these
Answer : A

11. Work done is a
A. Property of the system
B. Path function
C. Point function
D. State description of a system
Answer : B

12. Work done in case of free expansion is
A. Indeterminate
B. Zero
C. Negative
D. None of these
Answer : B

13. Chemical potential of ith component of a system is given by
A. ?_i = (?F/?n_i)_{T, P, ni}
B. ?_i = (?A/?n_i)_{T, P, ni}
C. ?_i = (?F/?n_i)_{T, P}
D. ?_i = (?A/?n_i)_{T, P}
Answer : A

14. If the heat of solution of an ideal gas in a liquid is negative, then its solubility at a given partial pressure varies with the temperature as
A. Solubility increases as temperature increases
B. Solubility increases as temperature decreases
C. Solubility is independent of temperature
D. Solubility increases or decreases with temperature depending on the Gibbs free energy change of solution
Answer : B

15. Lowering of condenser temperature (keeping the evaporator temperature constant) in case of vapour compression refrigeration system results in
A. Increased COP
B. Same COP
C. Decreased COP
D. Increased or decreased COP; depending upon the type of refrigerant
Answer : A

16. Fugacity co-efficient of a substance is the ratio of its fugacity to
A. Mole fraction
B. Activity
C. Pressure
D. Activity co-efficient
Answer : C

17. The thermodynamic law, PV^y = constant, is not applicable in case of
A. Ideal compression of air
B. Free expansion of an ideal gas
C. Adiabatic expansion of steam in a turbine
D. Adiabatic compression of a perfect gas
Answer : B

18. Reduced pressure of a gas is the ratio of its
A. Pressure to critical pressure
B. Critical pressure to pressure
C. Pressure to pseudocritical pressure
D. Pseudocritical pressure to pressure
Answer : A

19. Absolute zero temperature signifies the
A. Minimum temperature attainable
B. Temperature of the heat reservoir to which a Carnot engine rejects all the heat that is taken in
C. Temperature of the heat reservoir to which a Carnot engine rejects no heat
D. None of these
Answer : C

20. The equation, (d log_e PA/d log_e xA) = (d log_e PA/d log_e xB) applicable to a binary solution of components. A and B in equilibrium with their vapors at constant temperature and pressure is called the __________ equation.
A. Van Laar
B. Margules
C. Gibbs-Duhem
D. Gibbs-Duhem-Margules
Answer : D

21. When a gas is subjected to adiabatic expansion, it gets cooled due to
A. Decrease in velocity
B. Decrease in temperature
C. Decrease in kinetic energy
D. Energy spent in doing work
Answer : D

22. In a reversible chemical reaction (where, ?x = number of moles of products-number of moles of reactants)
A. Addition of inert gas favours the forward reaction, when ?x is positive
B. Pressure has no effect on equilibrium, when ?n = 0
C. Addition of inert gas has no effect on the equilibrium constant at constant volume for any value of ?x (+ ve, - ve) or zero)
D. All 'a', 'b' & 'c'
Answer : D

23. Pick out the wrong statement.
A. A refrigeration cycle violates the second law of thermodynamics
B. Refrigeration cycle is normally represented by a temperature vs. entropy plot
C. In a refrigerator, work required decreases as the temperature of the refrigerator and the temperature at which heat is rejected increases
D. One ton of refrigeration is equivalent to the rate of heat absorption equal to 3.53 kW
Answer : A

24. The following heat engine produces power of 100,000 kW. The heat engine operates between 800 K and 300 K. It has a thermal efficiency equal to 50% of that of the Carnot engine for the same temperature. The rate at which heat is absorbed from the hot reservoir is
A. 100,000 kW
B. 160,000 kW
C. 200,000 kW
D. 320,000 kW
Answer : D

25. Internal energy of an ideal gas
A. Increases with increase in pressure
B. Decreases with increase in temperature
C. Is independent of temperature
D. None of these
Answer : D

26. The four properties of a system viz. P, V, T, S are related by __________ equation.
A. Gibbs-Duhem
B. Gibbs-Helmholtz
C. Maxwell's
D. None of these
Answer : C

27. A refrigeration cycle is a reversed heat engine. Which of the following has the maximum value of the co-efficient of performance (COP) for a given refrigeration effect?
A. Vapor compression cycle using expansion valve
B. Air refrigeration cycle
C. Vapor compression cycle using expansion engine
D. Carnot refrigeration cycle
Answer : D

28. The internal energy of an ideal gas does not change in a reversible __________ process.
A. Isothermal
B. Adiabatic
C. Isobaric
D. Isometric
Answer : A

29. Heat is added at constant temperature in an ideal __________ cycle.
A. Stirling
B. Brayton
C. Rankine
D. None of these
Answer : A

30. Pick out the wrong statement.
A. At constant pressure, solubility of a gas in a liquid diminishes with rise in temperature
B. Normally, the gases which are easily liquefied are more soluble in common solvents
C. The gases which are capable of forming ions in aqueous solution are much more soluble in water than in other solvents
D. At constant pressure, solubility of a gas in a liquid increases with rise in temperature
Answer : A

31. 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

32. For an ideal liquid solution, which of the following is unity?
A. Activity
B. Fugacity
C. Activity co-efficient
D. Fugacity co-efficient
Answer : C

33. The value of C_p & C_v respectively for monatomic gases in Kcal/kg Mole.°K are
A. 5 & 3
B. 3.987 & 1.987
C. 1.987 & 0.66
D. 0.66 & 1.987
Answer : A

34. Which of the following is a thermodynamic property of a system?
A. Concentration
B. Mass
C. Temperature
D. Entropy
Answer : D

35. In a homogeneous solution, the activity coefficient of a component depends upon the
A. Pressure
B. Composition
C. Temperature
D. All (A), (B) and (C)
Answer : D

36. Two substances are in equilibrium in a reversible chemical reaction. If the concentration of each substance is doubled, then the value of the equilibrium constant will be
A. Same
B. Doubled
C. Halved
D. One fourth of its original value
Answer : A

37. Ideal refrigeration cycle is
A. Same as Carnot cycle
B. Same as reverse Carnot cycle
C. Dependent on the refrigerant's properties
D. The least efficient of all refrigeration processes
Answer : B

38. The activity of an ideal gas is numerically __________ its pressure.
A. More than
B. Less than
C. Equal to
D. Data insufficient, can't be predicted
Answer : C

39. During Joule-Thomson expansion of gases
A. Enthalpy remains constant
B. Entropy remains constant
C. Temperature remains constant
D. None of these
Answer : A

40. As the entropy of the universe is increasing, day by day, the work producing capacity of a heat engine is
A. Not changed
B. Decreasing
C. Increasing
D. Data sufficient, can't be predicted
Answer : B

41. The specific heat of saturated water vapour at 100°C is
A. ?
B. -ve
C. 0
D. +ve
Answer : B

42. Entropy change in case of reversible adiabatic process is
A. Minimum
B. Zero
C. Maximum
D. Indeterminate
Answer : B

43. 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

44. Air enters an adiabatic compressor at 300K. The exit temperature for a compression ratio of 3, assuming air to be an ideal gas (Y = C_p/C_v = 7/5) and the process to be reversible, is
A. 300 × (3^2/7)
B. 300 × (3^3/5)
C. 300 × (33^3/7)
D. 300 × (3^5/7)
Answer : A

45. For an ideal gas, the enthalpy
A. Increases with rise in pressure
B. Decreases with rise in pressure
C. Is independent of pressure
D. Is a path function
Answer : C

46. Charles' law for gases states that
A. V/T = Constant
B. V ? 1/T
C. V ? 1/P
D. PV/T = Constant
Answer : A

47. For the reversible exothermic reaction, N₂ + 3H₂ ? 2NH₃, increase of pressure would
A. Shift the equilibrium towards right
B. Give higher yield of NH₃
C. Both (B) and (C)
D. Neither (A) nor (B)
Answer : C

48. Specific volume of an ideal gas is
A. Equal to its density
B. The reciprocal of its density
C. Proportional to pressure
D. None of these
Answer : B

49. In a P-V diagram (for an ideal gas), an isothermal curve will coincide within adiabatic curve (through a point), when
A. C_p < C_v
B. C_p = C_v
C. C_p > C_v
D. C ? C_v
Answer : B

50. The amount of heat required to decompose a compound into its elements is __________ the heat of formation of that compound from its elements.
A. Less than
B. More than
C. Same as
D. Not related to
Answer : C