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.
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669 questions · page 19 of 34
- A. Temperature falls
- B. Pressure rises
- C. Temperature rises
- D. Pressure falls
Explanation: Relative humidity is the ratio of actual water-vapour pressure to saturation vapour pressure.
Correct answer: Temperature rises- A. 1
- B. < 1
- C. > 1
- D. 0
Explanation: Solvent selectivity is the ratio of the solvent's preference for the solute to its preference for the carrier.
Correct answer: > 1- A. None of these
- B. At > 210.6
- C. Between 100 and 210
- D. At < 100
Explanation: Immiscible liquids boil when the sum of their vapour pressures reaches atmospheric pressure.
Correct answer: At < 100- A. Synthetic zeolites crystals/metal alumino-silicates
- B. Silica
- C. Alumina
- D. None of these
Explanation: Molecular sieves are crystalline synthetic zeolites made from metal aluminosilicates.
Correct answer: Synthetic zeolites crystals/metal alumino-silicates- A. 1
- B. 2
- C. 3
- D. 4
Explanation: At the plait point, the compositions of the two liquid phases become identical and the tie-line length becomes zero.
Correct answer: 1- A. Nsc = 2
- B. Nst = 2
- C. Nsh = 2
- D. None of these
Explanation: For a spherical drop transferring mass by molecular diffusion into stagnant surroundings, the limiting Sherwood number is 2.
Correct answer: Nsh = 2- A. Both A. & B.
- B. Parallel
- C. Straight
- D. Neither A. nor B.
Explanation: Equality of overall and Murphree efficiencies follows when the graphical stage relationships do not change from tray to tray.
Correct answer: Both A. & B.- A. p >>P
- B. p = P
- C. p < P
- D. p << P
Explanation: Condensation starts when the vapour partial pressure reaches the saturation vapour pressure of the liquid at the same temperature.
Correct answer: p = P- A. Molal diffusivity
- B. Volumetric co-efficient
- C. Mass transfer co-efficient
- D. None of these
Explanation: A wetted-wall tower provides a known contact area between the phases, allowing the mass-transfer coefficient to be determined from…
Correct answer: Mass transfer co-efficient- A. Yes
- B. Yes; but the air flow rate should be excessively high
- C. Yes; but height of cooling tower will be prohibitively high
- D. No
Explanation: In a cooling tower, the lowest practical water temperature is limited by the entering air wet-bulb temperature.
Correct answer: No- A. 0.25
- B. 2.5
- C. 1.25
- D. 0.0025
Explanation: The diffusivity of water vapour in air near room temperature is approximately 0.25 cm²/s.
Correct answer: 0.25- A. Condenser and reboiler loads are the same in both the cases
- B. Both condenser and reboiler loads are higher in case (ii) as compared to case (i)
- C. Condenser load is the same in both the cases but reboiler load is higher in case (ii)
- D. Reboiler load is the same in both the cases but condenser load is higher in case (ii)
Explanation: Subcooled reflux must first be heated to its bubble point, increasing the reboiler duty, while the condenser must remove extra sensible…
Correct answer: Both condenser and reboiler loads are higher in case (ii) as compared to case (i)- A. Recovery of tannis from the tree barks and woods
- B. Leaching sodium nitrate from Chilean nitrate bearing rock
- C. Both A. and B.
- D. Neither A. nor B.
Explanation: The Shanks system is a countercurrent multiple-contact leaching process used for extracting tannins from bark and wood and for leaching…
Correct answer: Both A. and B.- A. Multiple effect evaporator
- B. Rotating disc contactor
- C. Rotary dryer
- D. Mechanical draft cooling tower
Explanation: A drift eliminator is fitted in a cooling tower to remove entrained water droplets from the leaving air and reduce water loss.
Correct answer: Mechanical draft cooling tower- A. Cold water leaving the tower and the wet bulb temperature of the surrounding air
- B. Hot water entering the tower and the wet bulb temperature of the surrounding air
- C. Hot water entering and the cooled water leaving the cooling tower
- D. None of these
Explanation: Cooling-tower approach is the temperature difference between the cooled water leaving the tower and the entering air wet-bulb temperature.
Correct answer: Cold water leaving the tower and the wet bulb temperature of the surrounding air- A. Inverse
- B. Linear
- C. Exponential
- D. Logarithmic
Explanation: At fixed temperature and pressure, humid volume is proportional to the amount of water vapour present, represented by humidity.
Correct answer: Linear- A. Less than
- B. Same as
- C. More than
- D. Very much less
Explanation: Flooding begins when the tray pressure drop exceeds the liquid head available in the downcomer, preventing liquid from flowing downward…
Correct answer: More than378. Which of the following is an undesirable characteristic for the solvent used in gas absorption ?
- A. Low vapor pressure
- B. Low viscosity
- C. None of these
- D. High gas solubility
Explanation: A good absorption solvent should have low vapour pressure and viscosity and high solubility for the absorbed gas.
Correct answer: None of these- A. Data insufficient, can't be predicted
- B. Decrease
- C. Remain same
- D. Increase
Explanation: Raising pressure generally lowers relative volatility for distillation systems, making separation more difficult.
Correct answer: Increase- A. Condenser and reboiler surfaces
- B. Area between operating line and 45° diagonal x-y diagram
- C. Tower cross-section
- D. None of these
Explanation: Increasing reflux moves the operating line closer to the 45° diagonal, so the area between them does not increase.
Correct answer: Area between operating line and 45° diagonal x-y diagram