Free Mass Transfer Operations MCQs with Answers
669 Mass Transfer Operations MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Last updated
669 questions · page 31 of 34
601. For gas absorption, low viscosity solvents are preferred, because of their ____________________?
- A. Better flow characteristics
- B. All A., B. and C.
- C. Rapid absorption rates
- D. Low pumping pressure drop
Explanation: Low-viscosity solvents flow more easily, require less pumping pressure, and offer lower liquid-film resistance, which increases absorption…
Correct answer: All A., B. and C.- A. Only heat
- B. Both heat and mass
- C. Only mass
- D. None of these
Explanation: Drying requires heat to vaporize moisture and mass transfer to move that vapour from the solid surface into the surrounding gas.
Correct answer: Both heat and mass- A. Liquid phase
- B. Gas phase
- C. Interface
- D. All A , B. & C.
Explanation: The gas and liquid compositions are assumed to be in equilibrium at their common interface when interfacial resistance is negligible.
Correct answer: Interface- A. More than
- B. Twice
- C. Equal to
- D. Half
Explanation: Packed towers are normally operated below flooding to maintain stable liquid distribution and avoid excessive entrainment and pressure…
Correct answer: Half- A. 100
- B. 10
- C. 5
- D. 1
Explanation: Penetration theory gives the liquid-side coefficient as proportional to the square root of the exposure frequency, and exposure frequency…
Correct answer: 10- A. Soap manufacturing
- B. Petroleum refining
- C. Polymerisation industry
- D. Ammonia synthesis plant
Explanation: Flash distillation is widely used in petroleum refining for rapid vaporisation and separation of crude-oil fractions.
Correct answer: Petroleum refining- A. Relative humidity decreases
- B. Relative humidity increases
- C. Both B. and C.
- D. Wet bulb temperature decreases
Explanation: Sensible cooling removes heat without changing the humidity ratio, so relative humidity rises as the air approaches saturation, while the…
Correct answer: Both B. and C.- A. NSc = NPr = NLe
- B. NSc = 1
- C. NPr = NLe
- D. NSc = NLe
Explanation: The concentration and temperature profiles coincide with the velocity profile when the Schmidt, Prandtl and Lewis numbers satisfy NSc =…
Correct answer: NSc = NPr = NLe609. In triangular co-ordinates, the ternary composition point falls ___________________ of the triangle?
- A. In the corners
- B. Inside
- C. On the sides
- D. None of these
Explanation: A ternary mixture with nonzero amounts of all three components is represented by a point inside the triangular composition diagram.
Correct answer: Inside- A. < 150
- B. > 500
- C. 200-330
- D. > 1000
Explanation: Molecular sieves are commonly regenerated by heating in roughly the 200 to 330°C range, often with a purge gas to remove the desorbed…
Correct answer: 200-330- A. Higher molecular weight is adsorbed in preference to a gas of low molecular weight
- B. High critical temperature is adsorbed in preference to a gas of low critical temperature
- C. Low volatility is adsorbed in preference to a gas of high volatility
- D. None of these
Explanation: Physical adsorption generally favours gases with higher molecular weight, higher critical temperature and lower volatility because these…
Correct answer: None of these- A. Both heating and humidification
- B. Heating only
- C. Humidification only
- D. Evaporative cooling
Explanation: The spray water at 40°C is warmer than the incoming air at 12°C, so the air gains sensible heat while water evaporates into it.
Correct answer: Both heating and humidification- A. Flow rate of the entering gas
- B. None of these
- C. Terminal concentrations of gas stream
- D. Composition of the entering liquid
Explanation: The entering gas flow rate, entering-liquid composition, and required terminal gas concentrations are all specified by the process duty.
Correct answer: None of these- A. None of these
- B. Vapour is recycled to the column
- C. Reboiler itself contains one plate
- D. Of the assumption that vapour and liquid leaving the reboiler are in equilibrium
Explanation: The reboiler is treated as one theoretical plate because its exiting vapour and liquid are assumed to reach equilibrium.
Correct answer: Of the assumption that vapour and liquid leaving the reboiler are in equilibrium- A. Increases
- B. Decreases
- C. Remain same
- D. Increases linearly
Explanation: During the constant-rate period, surface moisture evaporates and the rate is controlled mainly by external gas-side transfer.
Correct answer: Increases- A. Fluidised bed
- B. Spouted bed
- C. Tray
- D. Vacuum rotary
Explanation: Spouted-bed dryers are widely used for large-scale drying of grains such as wheat because they provide vigorous solids circulation and…
Correct answer: Spouted bed- A. Decreased liquid viscosity
- B. Increased diffusivity
- C. Both A. and B.
- D. Neither A. nor B.
Explanation: Higher temperature lowers the liquid viscosity, improving penetration and flow through the solid, while also increasing molecular…
Correct answer: Both A. and B.- A. q > 1
- B. q < 1
- C. q = 1
- D. q = 0
Explanation: For a saturated liquid feed, all feed enters the liquid phase, so the liquid flow added to the stripping section equals the feed flow.
Correct answer: q = 1- A. Lower than
- B. Higher than
- C. Same as
- D. Either same or higher than
Explanation: In adsorption hysteresis, capillary or pore-structure effects make desorption occur at a lower equilibrium pressure than adsorption at the…
Correct answer: Lower than- A. Greater than
- B. Smaller than
- C. Equal to
- D. Either A., or B.; depends on the type of packing
Explanation: Random packings generally flood at a lower gas velocity than well-designed stacked or structured packings, which offer more orderly flow…
Correct answer: Smaller than