1000+ Chemical Engineering Thermodynamics MCQ for GRE [Solved]

1. The temperature at which a real gas obeys the ideal gas laws over a wide range of pressure is called the __________ temperature.
A. Critical
B. Boyle
C. Inversion
D. Reduced
Answer : B

2. The number of degrees of freedom at the triple point of water is
A. 0
B. 1
C. 2
D. 3
Answer : A

3. With increase in temperature, the atomic heat capacities of all solid elements
A. Increases
B. Decreases
C. Remains unchanged
D. Decreases linearly
Answer : A

4. If two pure liquid constituents are mixed in any proportion to give an ideal solution, there is no change in
A. Volume
B. Enthalpy
C. Both (A) & (B)
D. Neither (A) nor (B)
Answer : C

5. Joule-Thomson Co-efficient at any point on the inversion curve is
A. ?
B. +ve
C. 0
D. -ve
Answer : C

6. A large iceberg melts at the base, but not at the top, because of the reason that
A. Ice at the base contains impurities which lowers its melting point
B. Due to the high pressure at the base, its melting point reduces
C. The iceberg remains in a warmer condition at the base
D. All (A), (B) and (C)
Answer : B

7. 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

8. High pressure steam is expanded adiabatically and reversibly through a well insulated turbine, which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ?H and ?S respectively for this process:
A. ? H = 0 and ?S = 0
B. ? H ? 0 and ?S = 0
C. ? H ? 0 and ?S ? 0
D. ? H = 0 and ?S ? 0
Answer : B

9. Consider the reaction, C + O₂ ? CO₂; ?H = - 94 kcal. What will be the value of ?H for the reaction CO₂ ? C + O₂?
A. -94 kcal
B. +94 kcal
C. > 94 kcal
D. < -94 kcal
Answer : B

10. The rate at which a substance reacts is proportional to its active mass and the rate of a chemical reaction is proportional to the product of active masses of the reacting substances. This is the
A. Lewis-Randall rule
B. Statement of Van't Hoff Equation
C. Le-Chatelier's principle
D. None of these
Answer : D

11. COP of a refrigerator drawing 1 kW of power per ton of refrigeration is about
A. 0.5
B. 3.5
C. 4.5
D. 8.5
Answer : B

12. The necessary condition for phase equilibrium in a multiphase system of N components is that the
A. Chemical potentials of a given component should be equal in all phases
B. Chemical potentials of all components should be same in a particular phase
C. Sum of the chemical potentials of any given component in all the phases should be the same
D. None of these
Answer : A

13. Which is not a refrigerant?
A. SO₂
B. NH₃
C. CCl₂F₂
D. C₂H₄Cl₂
Answer : D

14. If the pressure on 100 c.c. of air is halved, then its volume (at the same temperature) would be __________ c.c.
A. 100
B. 50
C. 205
D. 200
Answer : D

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

16. 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

17. Gibbs-Duhem equation
A. States that n₁d?₁ + n₂d?₂ + ....n_jd?_j = 0, for a system of definite composition at constant temperature and pressure
B. Applies only to binary systems
C. Finds no application in gas-liquid equilibria involved in distillation
D. None of these
Answer : A

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

19. The entropy change in a reversible isothermal process, when an ideal gas expands to four times its initial volume is
A. R log_e 4
B. R log₁₀ 4
C. C_v log₁₀ 4
D. C_v log_e 4
Answer : A

20. Pick out the wrong statement.
A. The values of (?P/?V)_T and (?²P/?V²)_T are zero for a real gas at its critical point
B. Heat transferred is equal to the change in the enthalpy of the system, for a constant pressure, non-flow, mechanically reversible process
C. Thermal efficiency of a Carnot engine depends upon the properties of the working fluid besides the source & sink temperatures
D. During a reversible adiabatic process, the entropy of a substance remains constant
Answer : C

21. The melting point of paraffin wax (which contracts on solidification) __________ with pressure rise.
A. Increases
B. Decreases
C. Remains unchanged
D. Decreases linearly
Answer : A

22. Joule-Thomson experiment is
A. Isobaric
B. Adiabatic
C. Isenthalpic
D. Both (B) & (C)
Answer : D

23. In case of vapour compression refrigeration system, elevating the evaporator temperature (keeping the condenser temperature constant) results in
A. Enhanced COP
B. Decreased COP
C. No change in the value of COP
D. Increased or decreased COP; depending upon the type of refrigerant
Answer : A

24. 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

25. Pick out the wrong statement.
A. The chemical potential of a pure substance depends upon the temperature and pressure
B. The chemical potential of a component in a system is directly proportional to the escaping tendency of that component
C. The chemical potential of ith species (?_i) in an ideal gas mixture approaches zero as the pressure or mole fraction (x_i) tends to be zero at constant temperature
D. The chemical potential of species 'i' in the mixture (?_i) is mathematically represented as,?_i = ?(nG)/?ni]_T,P,nj where, n, n_i and n_j respectively denote the total number of moles, moles of i^th species and all mole numbers except ith species. 'G' is Gibbs molar free energy
Answer : C

26. In case of a reversible process (following pvⁿ = constant), work obtained for trebling the volume (v1 = 1 m³ and v₂3 m³) is maximum, when the value of 'n' is
A. 0
B. 1
C. y = 1.44
D. 1.66
Answer : A

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 shape of T-S diagram for Carnot Cycle is a
A. Rectangle
B. Rhombus
C. Trapezoid
D. Circle
Answer : A

29. No work is done by the system, when a reaction occurs at constant
A. Volume
B. Temperature
C. Pressure
D. None of these
Answer : A

30. 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

31. Entropy change of the reaction, H2O (liquid) ? H2O (gas), is termed as the enthalpy of
A. Solution
B. Vaporisation
C. Formation
D. Sublimation
Answer : B

32. For the gaseous phase chemical reaction, C₂H₄(g) + H₂O(g) ? C₂H₅OH(g), the equilibrium conversion does not depend on the
A. Steam to ethylene ratio
B. Temperature
C. Pressure
D. None of these
Answer : D

33. The first law of thermodynamics is a restatement of the law of conservation of
A. Mass
B. Energy
C. Momentum
D. None of these
Answer : B

34. The theoretical minimum work required to separate one mole of a liquid mixture at 1 atm, containing 50 mole % each of n- heptane and noctane into pure compounds each at 1 atm is
A. -2 RT ln 0.5
B. -RT ln 0.5
C. 0.5 RT
D. 2 RT
Answer : B

35. Gibbs free energy (G) is represented by, G = H - TS, whereas Helmholtz free energy, (A) is given by, A = E - TS. Which of the following is the Gibbs-Helmholtz equation?
A. [?(G/T)/?T] = - (H/T₂)
B. [?(A/T)/?T]_V = - E/T₂
C. Both (A) and (B)
D. Neither (A) nor (B)
Answer : C

36. 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

37. In the reaction; N₂ + O₂ ? 2NO, increasing the pressure will result in
A. Shifting the equilibrium towards right
B. Shifting the equilibrium towards left
C. No change in equilibrium condition
D. None of these
Answer : C

38. A liquid under pressure greater than its vapour pressure for the temperature involved is called a __________ liquid.
A. Sub-cooled
B. Saturated
C. Non-solidifiable
D. None of these
Answer : A

39. Tea kept in a thermos flask is vigorously shaken. If the tea is considered as a system, then its temperature will
A. Increase
B. Decrease
C. Remain unchanged
D. First fall and then rise
Answer : A

40. Choose the condition that must be specified in order to liquify CO₂ (triple point for CO₂ is - 57°C and 5.2 atm).
A. Pressure must be kept below 5.2 atm
B. Temperature must be kept above - 57°C
C. Pressure must be kept below 5.2 atm. and temperature must be kept above 57°C
D. Pressure and temperature must be kept below 5.2 atm. and - 57°C respectively
Answer : D

41. Entropy of a substance remains constant during a/an __________ change.
A. Reversible isothermal
B. Irreversible isothermal
C. Reversible adiabatic
D. None of these
Answer : C

42. When liquid and vapour phase of multi-component system are in equilibrium (at a given temperature and pressure), then chemical potential of each component is
A. Same in both the phases
B. Zero in both the phases
C. More in vapour phase
D. More in liquid phase
Answer : A

43. The co-efficient of performance (COP) of a refrigerating system, which is its index of performance, is defined as the ratio of useful refrigeration to the net work. The units of __________ and COP are the same.
A. Kinematic viscosity
B. Work
C. Temperature
D. None of these
Answer : D

44. Throttling process is a/an __________ process.
A. Reversible and isothermal
B. Irreversible and constant enthalpy
C. Reversible and constant entropy
D. Reversible and constant enthalpy
Answer : B

45. For a reversible process involving only pressure-volume work
A. (dF)_T, p < 0
B. (dF)_T, p > 0
C. (dF)_T, p = 0
D. (dA)_T, v < 0
Answer : C

46. Claude's liquefaction process employs the cooling of gases by
A. Expansion in an engine
B. Following a constant pressure cycle
C. Throttling
D. None of these
Answer : A

47. 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

48. Compressibility factor of a gas is
A. Not a function of its pressure
B. Not a function of its nature
C. Not a function of its temperature
D. Unity, if it follows PV = nRT
Answer : A

49. 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

50. Pick out the Clausius-Clapeyron equation from the following:
A. dP/dT = ?H/T?V
B. ln P = - (?H/RT) + constant
C. ?F = ?H + T [?(?F)/?T]_P
D. None of these
Answer : B