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 5 of 34
- A. Drain the liquid from the tray when the unit is not in operation
- B. None of these
- C. Avoid back-trapping
- D. Allow for thermal expansion and facilitate installation
Explanation: The clearance between a tray and the column wall allows for thermal expansion and makes tray installation and removal possible.
Correct answer: Allow for thermal expansion and facilitate installation- A. More than
- B. Less than
- C. Same as
- D. Either more or less (depending upon relative volatility
Explanation: The stripping section commonly requires a larger diameter because its higher liquid traffic can increase the hydraulic loading and…
Correct answer: More than- A. Leads to high tray efficiency
- B. Results in higher pressure drop per tray
- C. Both A. & B.
- D. Neither A. or B.
Explanation: A deeper liquid layer generally improves vapour-liquid contact and tray efficiency, but it also increases the liquid head and therefore…
Correct answer: Both A. & B.- A. Downcomer liquid seal
- B. None of these
- C. Skirt clearance
- D. Static submergence
Explanation: Static submergence is the liquid depth above the top of the bubble-cap slots when the tray liquid is just at the overflow-weir level with…
Correct answer: Static submergence- A. A finite stage contactor
- B. Used only for distillation, not for absorption
- C. A differential stage contactor
- D. A continuous contactor
Explanation: A bubble-cap column provides contact on discrete trays, so it is a finite-stage or stagewise contactor.
Correct answer: A finite stage contactor- A. McCabe-Thiele's method
- B. Sorel-Lewis method
- C. Ponchon-Savarit method
- D. None of these
Explanation: Sorel-Lewis is an analytical stage-calculation method, whereas McCabe-Thiele and Ponchon-Savarit determine stages graphically.
Correct answer: Sorel-Lewis method87. Overall tray efficiency of a distillation column is the ratio of the number of ___________________?
- A. Overall gas transfer units to the number of ideal trays required
- B. Real trays required to the number of ideal trays required
- C. Ideal trays required to the number of real trays required
- D. None of these
Explanation: Overall tray efficiency compares the ideal number of stages with the actual number of trays: efficiency equals ideal trays divided by real…
Correct answer: Ideal trays required to the number of real trays required- A. IA. D2
- B. D9
- C. D
- D. D5
Explanation: For geometrically similar agitators operating at the same speed and fluid conditions, power varies approximately as the fifth power of…
Correct answer: D5- A. 0.07 - 0.12
- B. 0.01 - 0.5
- C. 0.5 - 1.0
- D. 1 - 3
Explanation: A typical tray pressure drop in an atmospheric distillation column is roughly 0.07 to 0.12 psi per tray.
Correct answer: 0.07 - 0.12- A. 2″-3.5″
- B. 0.5″ -1.25″
- C. 5″
- D. Half the tray spacing
Explanation: The liquid level should remain nearly uniform across a tray; the allowable gradient is approximately 0.5 to 1.25 inches.
Correct answer: 0.5″ -1.25″- A. 2.5
- B. 5
- C. 12.5
- D. 17.5
Explanation: A downcomer normally requires about 5 seconds of residence time to disengage entrained vapour and pass liquid smoothly to the tray below.
Correct answer: 5- A. 1
- B. 8
- C. 80
- D. 180
Explanation: A liquid residence time of about 8 seconds in the downcomer allows entrained vapour to disengage and provides stable liquid transfer to…
Correct answer: 8- A. All A., B. and C.
- B. Slope & length
- C. Flights arrangement
- D. rpm
Explanation: Material stays longer when the dryer rotates more slowly, is longer or more steeply inclined, and has flights that reduce its conveying…
Correct answer: All A., B. and C.- A. 45
- B. 60
- C. 80
- D. 95
Explanation: Sieve trays are commonly designed to operate at roughly 70 to 80% of flooding velocity, providing good vapour-liquid contact without…
Correct answer: 80- A. Less
- B. Same
- C. More
- D. Either A. or B.
Explanation: The frame must provide the space into which the filter cake forms, so its thickness is greater than the thickness of a filter plate.
Correct answer: More- A. 1/2 to 1/4th
- B. 1/5-1/10th
- C. 1/20-1/30th
- D. 1/10-1/15th
Explanation: To avoid excessive pressure drop and poor liquid distribution, random packing should be substantially smaller than the column diameter.
Correct answer: 1/10-1/15th- A. 6
- B. 12
- C. 18
- D. 36
Explanation: Large refinery columns commonly use tray spacings of about 18 inches as a practical minimum, allowing vapour disengagement and maintenance…
Correct answer: 18- A. Number of equilibrium stages in only stripping section is to be calculated
- B. Feed is not at its bubble point
- C. Relative volatility is close to one (e.g., separation of close boiling isomers)
- D. Number of equilibrium stages required is likely to be very small
Explanation: Smoker’s equation is useful for binary distillation when the relative volatility is close to unity, as in close-boiling mixtures.
Correct answer: Relative volatility is close to one (e.g., separation of close boiling isomers)- A. Molal flow rate of vapour
- B. Vapour molecular weight
- C. Pressure and temperature
- D. All A., B. and C.
Explanation: Pressure and temperature are higher at the tower bottom, while the heavier vapour composition and usually the vapour flow are also greater…
Correct answer: All A., B. and C.- A. η = 17 - 61.1 log μ
- B. η = 24.6 (Δp/μ)
- C. η = 1.66 - 0.25 log μ
- D. η = 0.25 log μ - 1.67
Explanation: For the stated viscosity and relative-volatility range, the refinery-column correlation is η = 17 − 61.1 log μ, with η expressed as a…
Correct answer: η = 17 - 61.1 log μ