chemical engineering mass transfer MCQs – Page 11

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 Review each marked answer and report any item that may be outdated or unclear.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
501. Humid volume, at a given temperature is a/an _______________ function of humidity?
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A. Logarithmic

B. Exponential

C. Inverse

D. Linear
502. In a distillation column, with increase in the reflux ratio, the heat removed in the cooler ______________________?
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A. Decreases

B. Remains unaffected

C. Increases

D. And the heat required in reboiler decreases

503. Tea percolation employs___________________________?
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A. Leaching

B. Liquid-liquid extraction

C. Absorption

D. None of these

504. Ordinary diffusion process is also called ______________ diffusion?
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A. Concentration

B. Pressure

C. Forced

D. Thermal

505. Steam distillation is used for separation of high boiling ____________________?
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A. Substances from non-volatile impurities

B. Volatile impurity from still higher boiling substances

C. Both A. and B.

D. Neither A. nor B.

506. During constant rate drying period, vaporisation rate per unit drying surface area _____________________?
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A. Does not change with time

B. Increases with time

C. Does not affect the moisture content of the wet solid

D. Decreases with time

507. Fractional solvent extraction______________________?
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A. Results in low interfacial tension

B. Employs only one solvent

C. None of these

D. Employs two solvents
508. Selectivity of the solvent used in solvent extraction should be)_________________?
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A. > 1

B. 1

C. < 1

D. 0

509. Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around _____________ inches?
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A. 100

B. 60

C. 30

D. 5

510. The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will______________________?
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A. Depend on saturated boiling point; may increase or decrease

B. Increase

C. Remain same

D. Decrease

511. During bottling of cold drinks (e.g. Pepsi), the main resistance to mass transfer for the absorption of carbon dioxide in water lies in the___________________?
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A. None of these

B. Liquid-gas interface

C. Liquid film

D. Gas film

512. When the ____________________ the relative humidity of air decreases, despite an increase in the absolute humidity?
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A. Temperature falls

B. Temperature rises

C. Pressure rises

D. Pressure falls

513. The efficiency of a plate column will be maximum, when the flow is ideal __________________ the plate?
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A. Across

B. Above

C. Both A. & B.

D. Neither A. nor B.

514. Flights in a rotary dryer are provided to________________?
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A. Reduce the residence time of solid

B. Increase the residence time of the solid

C. Lift and shower the solids thus exposing it thoroughly to the drying action of the gas

D. None of these

515. The relation, Sc = Pr = 1, is valid, when the mechanism of ______________ transfer is same?
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A. Heat and mass

B. Heat and momentum

C. Mass and momentum

D. Heat, momentum and mass

516. In the absorption of ammonia in water, the main resistance to absorption is by the _________________ phase?
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A. Liquid

B. Gas

C. Both A. & B.

D. Neither A. nor B.

517. Separation of a mixture of two gases by absorption in the liquid solvent depends upon the difference in their____________________?
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A. Density

B. Relative volatility

C. Solubility

D. Viscosity

518. In case of non-ideal gases and liquids, the molal diffusivity ________________?
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A. Is independent of pressure

B. Is equal to the volumetric diffusivity

C. Varies directly as the pressure

D. Varies inversely as the pressure

519. Which of the following is not a unit of mass transfer co-efficient ?
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A. Moles transferred/ [(time) (area) (pressure)]

B. None of these

C. Moles transferred/ [(time) (area) (mole fraction)]

D. Moles transferred/ [(time) (area) (mass A/mass B)]

520. Which of the following equipments is not used for liquid dispersion ?
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A. Wetted wall towers

B. Agitated vessels

C. Venturi scrubbers

D. Packed towers

521. Leaching of coffee from coffee beans is done by___________________?
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A. Dilute H2SO4 (hot)

B. Lime water

C. Hexane

D. Hot water
522. The solvent used in liquid extraction should not have high latent heat of vaporisation, because ______________________?
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A. It will decompose while recovering by distillation

B. Its recovery cost by distillation may be prohibitively high

C. It cannot be recovered by distillation

D. The pressure drop and hence the pumping cost will be very high

523. In most of the vacuum crystalliser, vacuum is generally produced by means of a_____________________?
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A. Steam jet ejector with a barometric condenser

B. None of these

C. Compressed air jet

D. Suction pump

524. Hypersorption refers to a ________________ process?
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A. Fixed bed absorption

B. Fixed bed adsorption

C. Moving bed absorption

D. Moving bed adsorption
525. If the overall efficiency and Murphree plate efficiency are equal, then both the equilibrium and operating lines are_______________?
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A. Straight

B. Parallel

C. Both A. & B.

D. Neither A. nor B.

526. A plait point is the point on the solubility curve, where the tie line reduces to a point. What is the number of plait point for a ternary system containing two pairs of partially miscible liquids ?
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A. 1

B. 0

C. 3

D. 2

527. Pick out the correct statement?
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A. None of these

B. Diffusivity increases with the size of the individual molecule

C. Diffusivity increases with increase in molecular weight

D. Diffusivity decreases with increase in temperature

528. If a two phase system is in physical equilibrium; then it means that, the_____________________?
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A. All A., B. and C.

B. al to that from vapor phase to liquid phase

C. Escaping tendency of each component from the liquid phase to the vapor phase is exactly

D. Total pressure throughout the liquid phase is equal to that throughout the vapor phase

E. Temperature of the liquid phase is equal to that of the vapor phase

529. Refractory bricks are usually dried in a ________________ dryer?
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A. Festoon

B. Conveyor

C. Tray

D. Tunnel
530. Pick out the wrong statement?
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A. Dehydration of ethyl alcohol is most economically done by molecular distillation at very high

B. Critical moisture content is not a property of the material itself

C. uum</strong>

D. Separation of components is not possible in liquid extraction, if selectivity is unity

E. A sharp increase in pressure drop gives an indication of the flooding in a distillation column

531. Ion exchange process is similar to___________________?
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A. Adsorption

B. Leaching

C. Absorption

D. Extraction

532. _____________ is the temperature at which a gas-vapor mixture becomes saturated, when cooled at constant total pressure out of contact with a liquid ?
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A. Dew point

B. Bubble point

C. Dry bulb temperature

D. Wet bulb temperature

533. The drying time between fixed moisture contents within the constant rate period is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid) ?
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A. ?T

B. T1.5

C. T

D. T3

534. _______________ developed the film theory ?
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A. Ergun

B. Fick

C. Higbie

D. Levenspiel

535. Pick out the wrong statement ?
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A. reases for a given L/V ratio

B. l column, in case of liquid-liquid extraction

C. tom

D. Natural draft cooling towers are made of ferroconcrete and its cross-section is wider at the

E. Vander wall adsorption is also called chemisorption

F. With decrease in feed temperature, the number of plates required for binary distillation

536. McCabe-Thiele method of binary distillation does not assume that the__________________?
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A. None of these

B. Heat of mixing is negligible

C. Sensible heat changes are negligible compared with latent heat changes

D. Molar latent heats of all components are equal

537. When the liquid over a plate is of uniform concentration, then ______________________?
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A. Murphree efficiency ? point efficiency

B. Murphree efficiency = point efficiency

C. Murphree efficiency > point efficiency

D. Murphree efficiency < point efficiency

538. As the reflux ratio decreases, the_________________?
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A. None of these

B. Column diameter increases

C. Separation becomes more efficient

D. Number of plates increases
539. The following plot gives the saturated humidity (He) versus temperature (T).Line joining (H1, T1) and (H2, T2) is the constant enthalpy line. Choose the correct one from among the alternatives A, B, C and D____________________?
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A. T1-Wet bulb temp; T2-Dry bulb temp; T3-Dew point temp

B. T1-Dew point temp; T2-Wet bulb temp; T3-Dry bulb temp

C. T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp

D. T1-Dew point temp; T2-Dry bulb temp; T3-Wet bulb temp

540. Entrainer used in Azeotropic distillation should____________________?
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A. Have high latent heat of vaporisation

B. Form a low boiling azeotrope with one of the constituents of the mixture

C. Have high viscosity to provide high tray efficiency

D. Form a new azeotrope of low relative volatility with one of the constituents of the mixture

541. If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement ?
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A. a1 = 2a2

B. a1 = 0.5 a2

C. a1 = a2

D. None of these
542. Pick out the correct statement ?
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A. Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the

B. tillation</strong>

C. A sharp decrease in pressure drop is an indication of flooding in a distillation coloumn

D. ber of theoretical stages required for the separation of non-ideal binary system by

E. Flash distillation is suitable for separating components which have very close boiling

F. perature

543. Pick out the wrong statement ?
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A. perature</strong>

B. Relative volatility of a binary mixture changes appreciably with the minor change in

C. Flash distillation is practised on wide spread scale in petroleum refinery

D. The relative volatility of a binary mixture at Azeotropic composition is unity

E. Constant pressure distillation cannot separate an Azeotropic mixture

544. An ideal tower packing should not _______________________?
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A. Have large surface area per unit volume

B. Hold up large amount of liquid in the packing

C. Have large free cross-section

D. Have low weight per unit volume

545. Heat load in a cooling tower______________________?
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A. Means the amount of heat thrown away (KCal/hr.) by the cooling tower

B. Is equal to the number of kg, of water circulated times the cooling range

C. Both A. & B.

D. Neither A. nor B.

546. _____________ temperature is the steady state temperature attained by a small amount of liquid evaporating into a large quantity of unsaturated gas-vapor mixture ?
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A. Wet bulb

B. Dry bulb

C. None of these

D. Dew point

547. The operating line for an absorber is curved, when plotted in terms of _______________________?
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A. Partial pressure

B. Mass fractions

C. Mole ratios

D. Mole fractions

548. Solvent used in extractive distillation_________________________?
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A. Is of low volatility

B. Does not alter the relative volatility of the original components

C. Forms a low boiling azeotrope

D. Forms a high boiling azeotrope

549. The dimension of diffusivity is same as that of the__________________?
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A. Molal concentration

B. Velocity head

C. Kinematic viscosity

D. dimension of diffusivity is same as that of the

E. Density

550. Occurrence of case hardening during drying of a high moisture solid cake _______________ the drying rate?
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A. Exponentially increases

B. Does not affect

C. Increases

D. Decreases