chemical engineering mass transfer Mcqs
651. When adsorption hysteresis is observed, the desorption equilibrium pressure is _________________ that obtained by adsorption?
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A. Always higher than

B. Same as

C. Dependent on the system; can be either lower or higher than

D. Always lower than
652. Berl saddle made of carbon cannot be used for ___________________?
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A. Oxidising atmosphere

B. Alkalis

C. H2SO4

D. SO2

653. In case of gases, the binary diffusivity is proportional to (where, P = pressure) ?
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A. 1/P

B. 1/?P

C. ?P

D. P

654. In saturated gas, the__________________?
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A. Vapour is in equilibrium with the liquid at the room temperature

B. None of these

C. Partial pressure of vapour equals the vapour pressure of the liquid at room temperature

D. Vapour is in equilibrium with the liquid at the gas temperature
655. Pick out the wrong statement?
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A. Change in barometric pressure does not affect the relative humidity

B. idity</strong>

C. erally

D. In case of a packed tower, the operating velocity is about half of the flooding velocity,

E. Elution means the desorption of the adsorbed solute by a solvent

F. The equilibrium moisture content of the solid can be reduced by increasing the absolute
656. Pick out the wrong statement pertaining to the cooling towers ?
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A. In case of induced draft cooling tower, the fan is placed at the top of the tower

B. A natural draft cooling tower is recommended to be used, when the air humidity is low and air

C. perature</strong>

D. Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and

E. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb

F. discharged air

657. Which of the following adsorbent is used in the refining of sugar?
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A. Silica gel

B. Wood charcoal

C. Activated clay

D. Bone charcoal
658. In extractive distillation, solvent is_____________________?
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A. Present in overhead stream

B. Of high volatility

C. Added to alter the relative volatility of the mixture

D. Of high viscosity to give high tray efficiency

659. For which of the following unit operations, Lewis number is of significance ?
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A. Humidification

B. Binary distillation

C. Gas absorption

D. Adsorption

660. Raoults law applies to the___________________?
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A. Non-volatile solute

B. Solvents

C. Non-ideal solution only

D. All liquid solutions

661. Weight of 1 m3 of humid air as compared to 1 m3 of dry air, under the same conditions, is_________________?
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A. More

B. Same

C. Unpredictable

D. Less
662. Percentage saturation is _______________ the relative saturation?
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A. Always smaller than

B. Not related to

C. Always greater than

D. None of these

663. In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because_______________?
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A. dition</strong>

B. Total pressure is less

C. Temperature is less

D. Mixing of steam with the material being vaporised is not so intimate as to result in equilibrium

E. Saturated steam is used for steam distillation

664. Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when____________________?
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A. One of the liquid components is heat sensitive

B. Extracting solvent is cheaply & abundantly available

C. Viscosity of liquid components is very high

D. One of the liquid components has very high affinity towards the solvent
665. In an absorber, HETP does not vary with the____________________?
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A. None of these

B. Flow rate of gas

C. Flow rate of liquid

D. Type and size of packing

666. Pick out the wrong statement?
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A. oding is generally encountered in packed towers

B. Packed towers are preferred over plate towers for handling corrosive and foamy liquids

C. Due to uneven supply and improper distribution of liquid, problem of channelling, loading &

D. Packed towers are preferred for vacuum operation, because the pressure drop through the

E. Diameter of randomly packed tower is normally more than 1.2 metres

F. king is less and they (packings) also lessen the possibility of tower wall collapse

667. Pick out the wrong statement?
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A. Molecular diffusion in solid is much faster than that in liquids

B. Particles movement from higher concentration to lower concentration takes place in diffusion

C. w of a gas through a given capillary

D. According to Poiseuilles law, the permeability decreases with increase in temperature for

E. The binary diffusivity in liquids is of the order of 10-5 cm2/sec

F. cess

668. The term cooling range in a cooling tower refers to the difference in the temperature of____________________?
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A. Hot water entering the tower and the wet bulb temperature of the surrounding air

B. Cold water leaving the tower and the wet bulb temperature of the surrounding air

C. None of these

D. Hot water entering the tower and the cooled water leaving the tower
669. Drying operation under vacuum is carried out to __________________?
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A. Dry materials having high bound moisture content

B. Increase drying temperature

C. Dry those materials which have very high unbound moisture content

D. Reduce drying temperature
670. Pick out the correct statement ?
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A. All A., B. and C.

B. reases

C. With increase in temperature, the selectivity of the solvent used in solvent extraction

D. d is unity

E. The selectivity of solvent used in solvent extraction is unity at the plait point

F. In case of liquid-liquid extraction, no separation is possible, if the selectivity of the solvent

671. The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are __________________?
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A. Parallel

B. Straight

C. Both parallel and straight

D. Neither parallel nor straight

672. Hydrogenation of oil is carried out in a/an _______________ in Vanaspati manufacturing plant?
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A. Sieve tray column

B. Packed tower

C. Bubble cap column

D. Agitated vessel
673. Boiling point diagram is not affected by the ambient______________________?
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A. Pressure

B. Humidity

C. Temperature

D. Both B. and C.
674. On addition of solute in the solvent, the ______________ of the solution decreases ?
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A. Boiling point

B. Freezing point

C. Vapour pressure

D. Both B. and C.
675. A packed tower compared to a plate tower for a particular mass transfer operation__________________?
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A. Allows installation of cooling coils

B. Is less costly when built in large sizes/diameters

C. Is more suitable, if suspended solids are present in fluid streams

D. Incurs smaller pressure drop
676. For continuous drying of granular or crystalline material, the dryer used is the _______________ dryer?
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A. Rotary

B. Tunnel

C. None of these

D. Tray

677. At a fixed total pressure, humidity depends only on the _______________________?
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A. None of these

B. Density of the vapour

C. Partial pressure of vapour in the mixture

D. Heat capacity of the vapour

678. Rate of leaching increases with increasing______________________?
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A. Size of the solid

B. Pressure

C. Viscosity of solvent

D. Temperature
679. The rate of solid-liquid extraction is limited by the_________________?
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A. Phase change of the solute as it dissolves in the solvent

B. Diffusion of the solute from the solution in contact with the particle to the main bulk of the

C. ution

D. Diffusion of the solute through the solvent in the pores to the outside of the particle

E. All A , B. & C.
680. Extraction of penicillin employs a ________________ extraction column?
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A. Plate

B. Centrifugal

C. Packed

D. None of these

681. Ponchon-Savarit method analyses the fractional equipment based on___________________?
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A. Enthalpy balance only

B. Material balance only

C. Both enthalpy and material balances

D. The assumption of constant molal-overflow

682. Diffusivity in concentrated solutions differs from that in dilute solutions, because of the changes in ____________________?
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A. Viscosity with concentration

B. Degree of ideality of the solution

C. Both A. and B.

D. Neither A. nor B.

683. In a counter-current extractor, as the axial mixing increases, the extraction efficiency______________________?
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A. Remains unchanged

B. Increases

C. Decreases

D. Depends on the pressure of the system

684. A mixture of 10% C6H6 vapour in air at 25C and 750 mm Hg has a dew point of 20C. Its dew point at 30C and 700 mm Hg will be around _______________ C?
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A. 27.3

B. 18.7

C. 20

D. 21.7

685. In case of an absorber, the operating _______________?
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A. Line always lies above the equilibrium curve

B. Velocity is more than the loading velocity

C. Line can be either above or below the equilibrium curve

D. Line always lies below the equilibrium curve

686. Air at a particular humidity is heated in a furnace. The new dew point_____________________?
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A. Decreases

B. Remain unchanged

C. Increases

D. Depends on the extent of heating

687. Channelling in a packed tower results from the_____________________?
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A. High pressure drop

B. Maldistribution of liquid

C. Non-uniformity of packing

D. Both B. and C.
688. Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent ______________________?
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A. A binary mixture

B. A ternary mixture

C. A pure component

D. Partially miscible ternary system

689. In a binary system, separation is very efficient, when the relative volatility is_______________?
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A. > 1

B. < 1

C. 1

D. 0.5

690. Which of the following same diameter columns gives lowest pressure drop per unit height ?
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A. Packed column (stacked)

B. Randomly packed column

C. Bubble-cap column

D. Sieve-plate column

691. The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = _________________?
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A. 1

B. 0

C. 10

D. 0.5

692. Langmuir equation is associated with________________________?
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A. Adsorption

B. Multi-component absorption

C. Leaching

D. Steam distillation

693. The minimum number of theoretical plates is required for achieving a given separation in distillation column with_________________?
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A. No reflux

B. Zero reflux ratio

C. Minimum reflux ratio

D. Total reflux
694. As the reflux ratio in a distillation column is increased from the minimum, the______________________?
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A. Total cost first decreases and then increases

B. Slope of the operating line in stripping section decreases

C. Number of plates decreases very slowly first and then more and more rapidly

D. Liquid flow increases while the vapor flow decreases for a system

695. For the same process conditions, the reflux ratio of an unlagged distillation column___________________?
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A. Increases in summer

B. Increases in winter

C. Decreases in winter

D. None of these

696. Critical humidity of a solid salt means the humidity_____________________?
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A. Above which it will always become damp

B. Below which it will always stay dry

C. Both A. and B.

D. Above Which it will always become dry and below which it will always stay damp

697. Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty ?
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A. Bubble cap column

B. Randomly packed column

C. Wetted wall column

D. Sieve plate column