chemical engineering mass transfer MCQs – Page 32

Practise multiple-choice questions from chemical engineering mass transfer for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering mass transfer Mcqs

621. Absorption factor method is used to calculate the number of ideal stages, when_______________________?
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A. Operating line lies above the equilibrium line

B. Operating line lies below the equilibrium line

C. Both operating and equilibrium lines are parallel

D. Pressure drop in the column is very high

622. Chemisorption (chemical adsorption) is_______________________?
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A. A reversible phenomenon

B. Same as Van der Waals adsorption

C. Characterised by adsorption of heat

D. An irreversible phenomenon

623. Pick out the wrong statement?
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A. In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated

B. In small columns, local efficiency is larger than Murphree efficiency; in large columns local

C. The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness,

D. For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L

E. m the leading edge is 1.5 10-2m/s. Then the average mass transfer co-efficient for the

F. Schmidt number is equal to unity

624. Pick out the correct statement?
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A. The sum of free moisture and equilibrium moisture in a solid is called the critical moisture

B. The driving force for mass transfer in a wet solid is its free moisture content

C. Free moisture is removed during falling rate drying period

D. Bound moisture is removed during constant rate drying period

625. What is the reflux ratio at total reflux ?
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A. Unity

B. Infinity

C. Data insufficient

D. Zero

626. Pick out the wrong statement ?
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A. For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both

B. The relative volatility of a binary mixture at the Azeotropic composition is 1

C. Azeotropes obey Raoults law at all temperature

D. ponents is nonlinear in the case of steady state unimolal unidirectional diffusion

E. The mole fraction of solute is directly proportional to the molality of a dilute solution

627. Solvent used in extractive distillation___________________?
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A. All A., B. and C.

B. Should be of high volatility

C. Should form azeotropes with the original components

D. Changes the relative volatility of the original components

628. Which of these columns incurs the lowest pressure drop ?
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A. Packed column (with stacked packing)

B. Bubble plate column

C. Pulse column

D. Packed column (with dumped packing)

629. An Azeotropic mixture is a ________________ mixture?
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A. Ternary

B. Binary

C. None of these

D. Constant boiling point

630. At equilibrium the concentration of water in vapour phase (C*) in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C* = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is_________________?
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A. 0

B. 0.2

C. 1

D. 0.4

631. Dryer widely used in a textile industry is ______________ dryer?
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A. Tunnel

B. Cylinder

C. Conveyor

D. Festoon

632. The binary diffusivity in gases at atmospheric conditions is about ___________________?
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A. 10-3 sec/cm

B. 10-4 cm2/sec2

C. 10-1 cm2/sec

D. 10-9 cm/sec

633. Which of the following parameters remains almost constant during adiabatic saturation of unsaturated air ?
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A. None of these

B. Dew point

C. Dry bulb temperature

D. Wet bulb temperature

634. Pick out the correct statement ?
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A. ked tower

B. All A., B. and C.

C. uid hold up is more in the case of plate column

D. Plate column can handle greater liquid loads without flooding than packed column, but the

E. For identical gas flow rates, less pressure drop occurs through a plate tower than through a

F. For the same duty, plate columns weigh less than packed columns

635. Pick out the wrong statement pertaining to the rotary dryer ?
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A. Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it

B. Rotary dryer is suitable for drying sticky material

C. n through the current of hot air/gases. It extends from the wall to a distance which is about

D. 2% of the inside diameter of shell

E. instant. The best performance for rotary drier is obtained, when the hold up is in the range

F. Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at

636. Total reflux in a distillation operation requires minimum____________________?
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A. Reboiler load

B. Condenser load

C. All A., B. and C.

D. Number of plates

637. CO2 can be absorbed by____________________?
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A. Alumina

B. Heated charcoal

C. Hot cupric oxide

D. Cold Ca(OH)2

638. Schmidt number is given by ___________________?
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A. Re Pe

B. Sh Pe

C. ?/?DAB

D. Re/Pe

639. In case of liquid-liquid binary diffusion, diffusivity of one constituent into another is not dependent on the__________________?
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A. Temperature and pressure

B. Concentration

C. Nature of the constituents

D. None of these

640. For a binary mixture with low relative volatility, continuous rectification to get pure products will require_____________________?
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A. Low reflux ratio

B. Less number of trays

C. Small cross-section column

D. High reflux ratio

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