Chemical Engineering Mass Transfer MCQ - Set 06 - ObjectiveBooks

# Practice Test: Question Set - 06

1. The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the
(B) Heat of wetting
(D) None of these

2. A 25 cm × 25 cm × 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m × 1m × 1cm flat sheet of the same material is to be dried from one side only. Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is
(A) 1000
(B) 1500
(C) 2000
(D) 2500

3. Moisture in a solid exerting an equilibrium vapor pressure equal to that of the pure liquid at the same temperature is called the __________ moisture.
(A) Unbound
(B) Critical
(C) Free
(D) Bound

4. Swenson-Walker crystallizer is a __________ unit.
(A) Continuous
(B) Batch
(C) Semi-batch

5. For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be
(A) 1
(B) 0
(C) 2
(D) 3

6. Calculation of mass transfer co-efficient is mostly/normally done using __________ theory.
(A) Surface renewal
(B) Film
(C) Penetration
(D) None of these

7. With increase in temperature, the leaching rate increases because of the
(A) Increased diffusivity
(B) Decreased viscosity of liquid
(C) Both (a) and (b)
(D) Neither (a) nor (b)

8. Relative volatility varies with the concentration of component for an ideal solution. The relative volatility of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when
(A) Only vapor phase follows Raoult's law
(B) Only liquid phase obeys Dalton's law
(C) Liquid phase obeys Dalton's law and vapor phase obeys Raoult's law
(D) Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law

9. Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes?
(A) Packed towers
(B) Plate towers
(C) Spray towers
(D) Wetted wall columns

10. Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as
(A) K D
(B) K D
(C) K D1.5
(D) K D2

11. Pick out the wrong statement.
(A) Mechanical agitation is required, if the system has low interfacial tension
(B) Sieve tray towers are generally used for systems having low interfacial tension
(C) When Henry's law constant is very small, then the mass transfer rate is controlled by the gas film resistance
(D) Taylor-Prandtl analogy for heat and mass transfer considers the transfer through both laminar and turbulent layers

12. For water-ethanol system, the minimum reflux ratio
(A) Is computed from the slope of the upper operating line that is tangent to the equilibrium curve
(B) Is computed from the intercept of the operating line
(C) Cannot be computed
(D) Is the optimum reflux ratio

13. Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation?
(A) Cost
(B) Availability
(C) Toxicity
(D) Selectivity

14. At 750°K and 1 atm, the approximate value of Schmidt number for air is
(A) 0.01
(B) 0.1
(C) 1
(D) 10

15. What is the degree of freedom of an absorption process in which only one component is transferred between phases?
(A) 1
(B) 2
(C) 3
(D) 4

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