L/mG is the expression for

slope of operating line in absorber

slope of operating line in stripper.

Drift in a cooling tower is

dependent on the water lost by evaporation.

the water entrained by the circulating air.

dependent on the water lost by evaporation.

Flash distillation is

same as differential distillation.

used for multicomponent systems like crude refining.

most useful for handling binary systems.

Inside the distillation columns, the

vapors are not always at their dew points.

highest temperatures is near the feed plate.

driving force for the liquid flow is its weight.

vapors are not always at their dew points.

In case of a desorber (stripper), the

temperature remains unaffected.

operating line always lies above the equilibrium curve.

operating line always lies below the equilibrium curve.

temperature remains unaffected.

Pick out the wrong statement. Generally for physical adsorption, a gas of

higher molecular weight is adsorbed in preference to a gas of low molecular weight.

high critical temperature is adsorbed in preference to a gas of low critical temperature.

low volatility is adsorbed in preference to a gas of high volatility.

For stripping of a gas in a counter current stripper, the operating line

is always parallel to the equilibrium curve.

lies above the equilibrium curve.

lies below the equilibrium curve.

can lie above or below the equilibrium curve.

is always parallel to the equilibrium curve.

Mass transfer co-efficient is defined as

Flux=concentration difference/co-effi-cient.

Flux = Co-efficient/concentration difference.

Co-efficient = Flux/concentration difference.

Flux=concentration difference/co-effi-cient.

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because

saturated steam is used for steam distillation.

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

saturated steam is used for steam distillation.

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of

momentum diffusivity to thermal diffusivity.

mass diffusivity to momentum diffusivity.

thermal diffusivity to mass diffusivity.

momentum diffusivity to thermal diffusivity.

For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates.

binary mixture is represented by the apex

binary mixture is represented by any point inside

ternery mixture is represented by the sides

pure component is represented by the apex.

is a function of the mass transfer between liquid and vapour.

increases due to liquid entrainment.

increases due to weeping and dumping of liquid.

Swenson-Walker crystalliser is a __________ unit

cooling (adiabatic)-cum-evaporation

Which of the following solutions will follow Raoult's law most closely ?

35% solution of camphor in water.

A solution of benzene, toluene and oxylene.

35% solution of camphor in water.

A solution of polar organic compounds (not of homologs of a series).

Flights in a rotary dryer are provided to

reduce the residence time of solid.

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

reduce the residence time of solid.

increase the residence time of the solid.

In most of the vacuum crystalliser, vacuum is generally produced by means of a

steam jet ejector with a barometric condenser

Dew point of an air-water vapor mixture

decreases with decrease in pressure.

at constant humidity & total pressure is fixed.

corresponding to any point on the humidity chart is obtained by projecting a line through this point parallel to the temperature axis and to the saturation curve.

854 + Mcqs in Mass Transfer in Chemical Engineering Page 10 McqOptions

451.	L/mG is the expression for
A.	absorption factor
B.	Brinkman number
C.	slope of operating line in absorber
D.	slope of operating line in stripper.
Answer» B. Brinkman number

Discussion

452.	In an absorber, HETP does not vary with the
A.	flow rate of liquid
B.	flow rate of gas
C.	type and size of packing
D.	none of these
Answer» E.

Discussion

453.	Drift in a cooling tower is
A.	the water entrained by the circulating air.
B.	dependent on the water lost by evaporation.
C.	desirable.
D.	all (a), (b) & (c).
Answer» B. dependent on the water lost by evaporation.

Discussion

454.	(NRe . NSc) is termed in mass transfer operation as the __________ number.
A.	Stanton
B.	Sherwood
C.	Peclet
D.	none of these
Answer» D. none of these

Discussion

455.	The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2/m3)
A.	500
B.	1200
C.	900
D.	800
Answer» B. 1200

Discussion

456.	Flash distillation is
A.	same as differential distillation.
B.	used for multicomponent systems like crude refining.
C.	same as simple distillation.
D.	most useful for handling binary systems.
Answer» C. same as simple distillation.

Discussion

457.	Use of natural draft cooling tower is practised, when the air has low
A.	humidity
B.	temperature
C.	both 'a' & 'b'
D.	neither 'a' nor 'b'
Answer» D. neither 'a' nor 'b'

Discussion

458.	Inside the distillation columns, the
A.	highest temperatures is near the feed plate.
B.	driving force for the liquid flow is its weight.
C.	vapors are not always at their dew points.
D.	all (a), (b) and (c)
Answer» C. vapors are not always at their dew points.

Discussion

459.	In case of a desorber (stripper), the
A.	operating line always lies above the equilibrium curve.
B.	operating line always lies below the equilibrium curve.
C.	temperature remains unaffected.
D.	temperature always increases.
Answer» C. temperature remains unaffected.

Discussion

460.	Pick out the wrong statement. Generally for physical adsorption, a gas of
A.	higher molecular weight is adsorbed in preference to a gas of low molecular weight.
B.	high critical temperature is adsorbed in preference to a gas of low critical temperature.
C.	low volatility is adsorbed in preference to a gas of high volatility.
D.	none of these.
Answer» E.

Discussion

461.	According to Chilton-Colburn analogy for mass transfer, NSt.NSc2/3 is equal to
A.	f
B.	f/2
C.	2f
D.	1/f
Answer» C. 2f

Discussion

462.	For stripping of a gas in a counter current stripper, the operating line
A.	lies above the equilibrium curve.
B.	lies below the equilibrium curve.
C.	can lie above or below the equilibrium curve.
D.	is always parallel to the equilibrium curve.
Answer» D. is always parallel to the equilibrium curve.

Discussion

463.	Dimension of mass diffusivity is the same as that of
A.	kinematic viscosity
B.	dynamic viscosity
C.	surface tension
D.	pressure
Answer» B. dynamic viscosity

Discussion

464.	Leaching rate is independent of the
A.	agitation
B.	temperature
C.	particle size
D.	none of these
Answer» E.

Discussion

465.	Diameter to height ratio for a rashig ring is
A.	1
B.	0.5
C.	2
D.	8
Answer» B. 0.5

Discussion

466.	Lewis number (Le) is
A.	Sc x Pr
B.	Pr x St
C.	Sh x Pr
D.	St x Sh
Answer» B. Pr x St

Discussion

467.	Which of the following increases during evaporative cooling process with recirculated water supply ?
A.	Wet bulb temperature
B.	Relative humidity
C.	Partial pressure of vapour
D.	Both (b) and (c)
Answer» E.

Discussion

468.	With increase in temperature, the mutual solubility of two liquids
A.	increases
B.	decreases
C.	remains unchanged
D.	decreases exponentially
Answer» B. decreases

Discussion

469.	Azeotropism for ethyl alcohol-water system disappears by
A.	increasing temperature
B.	decreasing pressure
C.	increasing pressure
D.	no means
Answer» C. increasing pressure

Discussion

470.	__________ is concerned with the adsorption equilibria.
A.	Fick's law
B.	Gibb's equation
C.	Freundlich equation
D.	none of these
Answer» D. none of these

Discussion

471.	Leaching of sugar from sugar beets is done by
A.	hot water
B.	hexane
C.	dilute H2SO4
D.	lime water
Answer» B. hexane

Discussion

472.	Mass transfer co-efficient is defined as
A.	Flux = Co-efficient/concentration difference.
B.	Co-efficient = Flux/concentration difference.
C.	Flux=concentration difference/co-effi-cient.
D.	none of these.
Answer» C. Flux=concentration difference/co-effi-cient.

Discussion

473.	In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because
A.	temperature is less.
B.	total pressure is less.
C.	mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.
D.	saturated steam is used for steam distillation.
Answer» D. saturated steam is used for steam distillation.

Discussion

474.	Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.
A.	molal
B.	relative
C.	percentage
D.	none of these
Answer» B. relative

Discussion

475.	Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.
A.	wetted wall
B.	bubble cap
C.	perforated tray
D.	packed
Answer» B. bubble cap

Discussion

476.	Which of the following is the most commonly used leaching solvent in vegetable oil industry ?
A.	Phenol
B.	Hexane
C.	Furfurol
D.	Liquid SO2
Answer» C. Furfurol

Discussion

477.	Refractory bricks are usually dried in a __________ dryer.
A.	tray
B.	tunnel
C.	conveyor
D.	festoon
Answer» C. conveyor

Discussion

478.	Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of
A.	mass diffusivity to momentum diffusivity.
B.	thermal diffusivity to mass diffusivity.
C.	momentum diffusivity to thermal diffusivity.
D.	none of these.
Answer» C. momentum diffusivity to thermal diffusivity.

Discussion

479.	For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates.
A.	binary mixture is represented by the apex
B.	binary mixture is represented by any point inside
C.	ternery mixture is represented by the sides
D.	pure component is represented by the apex.
Answer» E.

Discussion

480.	Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches.
A.	5
B.	30
C.	60
D.	100
Answer» C. 60

Discussion

481.	Selectivity of the solvent used in solvent extraction should be
A.	1
B.	> 1
C.	< 1
D.	0
Answer» C. < 1

Discussion

482.	__________ column is used in gas absorption process.
A.	Wetted wall
B.	Seive/perforated tray
C.	Bubble cap
D.	Packed
Answer» E.

Discussion

483.	If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is
A.	L/G
B.	G/L
C.	always < 1
D.	none of these
Answer» B. G/L

Discussion

484.	(NSh/NRe.NSc) is termed in mass transfer operation as the
A.	Stanton number
B.	Peclet number
C.	thermal diffusivity
D.	momentum diffusivity
Answer» B. Peclet number

Discussion

485.	Plate efficiency
A.	is a function of the mass transfer between liquid and vapour.
B.	increases due to foaming.
C.	increases due to liquid entrainment.
D.	increases due to weeping and dumping of liquid.
Answer» B. increases due to foaming.

Discussion

486.	In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of
A.	1.5
B.	-0.6
C.	-1.5
D.	0.6
Answer» D. 0.6

Discussion

487.	Operating velocity in a packed tower is usually __________ the flooding velocity.
A.	half
B.	twice
C.	equal to
D.	more than
Answer» B. twice

Discussion

488.	Swenson-Walker crystalliser is a __________ unit
A.	continuous
B.	batch
C.	semi-batch
D.	cooling (adiabatic)-cum-evaporation
Answer» B. batch

Discussion

489.	Schmidt number is given by
A.
B.	Re.Pe
C.	Sh x Pe
Answer» B. Re.Pe

Discussion

490.	Which of the following solutions will follow Raoult's law most closely ?
A.	A solution of benzene, toluene and oxylene.
B.	35% solution of camphor in water.
C.	35% solution of NH3 in water.
D.	A solution of polar organic compounds (not of homologs of a series).
Answer» B. 35% solution of camphor in water.

Discussion

491.	__________ equation applies to diffusivities in liquids.
A.	Gilliland
B.	Hirschfelder
C.	Wilke and Chang
D.	none of these
Answer» B. Hirschfelder

Discussion

492.	Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)
A.	(De.t)1/2
B.	(De/t)1/2
C.	(4De/œÄt)1/2
D.	(4De/t)
Answer» D. (4De/t)

Discussion

493.	Rate of leaching increases with increasing
A.	temperature
B.	viscosity of solvent
C.	pressure
D.	size of the solid
Answer» B. viscosity of solvent

Discussion

494.	Flights in a rotary dryer are provided to
A.	lift and shower the solids thus exposing it thoroughly to the drying action of the gas.
B.	reduce the residence time of solid.
C.	increase the residence time of the solid.
D.	none of these.
Answer» B. reduce the residence time of solid.

Discussion

495.	In most of the vacuum crystalliser, vacuum is generally produced by means of a
A.	suction pump
B.	compressed air jet
C.	steam jet ejector with a barometric condenser
D.	none of these
Answer» D. none of these

Discussion

496.	Coffee is prepared from coffee beans by leaching with
A.	cold water
B.	hot water
C.	dilute hot caustic solution
D.	naphtha
Answer» C. dilute hot caustic solution

Discussion

497.	Minimum reflux ratio in a distillation column results in
A.	optimum number of trays.
B.	minimum reboiler size.
C.	maximum condenser size.
D.	minimum number of trays.
Answer» D. minimum number of trays.

Discussion

498.	Water entrained by circulating air in cooling towers is termed as
A.	drift
B.	blow down
C.	vapor load
D.	none of these.
Answer» B. blow down

Discussion

499.	Dew point of an air-water vapor mixture
A.	decreases with decrease in pressure.
B.	at constant humidity & total pressure is fixed.
C.	corresponding to any point on the humidity chart is obtained by projecting a line through this point parallel to the temperature axis and to the saturation curve.
D.	all 'a', 'b' & 'c'.
Answer» E.

Discussion

500.	__________ developed the film theory.
A.	Higbie
B.	Fick
C.	Ergun
D.	Levenspeil
Answer» B. Fick

Discussion

Explore topic-wise MCQs in Chemical Engineering.

L/mG is the expression for

In an absorber, HETP does not vary with the

Drift in a cooling tower is

(NRe . NSc) is termed in mass transfer operation as the __________ number.

The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2/m3)

Flash distillation is

Use of natural draft cooling tower is practised, when the air has low

Inside the distillation columns, the

In case of a desorber (stripper), the

Pick out the wrong statement. Generally for physical adsorption, a gas of

According to Chilton-Colburn analogy for mass transfer, NSt.NSc2/3 is equal to

For stripping of a gas in a counter current stripper, the operating line

Dimension of mass diffusivity is the same as that of

Leaching rate is independent of the

Diameter to height ratio for a rashig ring is

Lewis number (Le) is

Which of the following increases during evaporative cooling process with recirculated water supply ?

With increase in temperature, the mutual solubility of two liquids

Azeotropism for ethyl alcohol-water system disappears by

__________ is concerned with the adsorption equilibria.

Leaching of sugar from sugar beets is done by

Mass transfer co-efficient is defined as

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because

Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.

Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.

Which of the following is the most commonly used leaching solvent in vegetable oil industry ?

Refractory bricks are usually dried in a __________ dryer.

Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of

For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates.

Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches.

Selectivity of the solvent used in solvent extraction should be

__________ column is used in gas absorption process.

If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is

(NSh/NRe.NSc) is termed in mass transfer operation as the

Plate efficiency

In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of

Operating velocity in a packed tower is usually __________ the flooding velocity.

Swenson-Walker crystalliser is a __________ unit

Schmidt number is given by

Which of the following solutions will follow Raoult's law most closely ?

__________ equation applies to diffusivities in liquids.

Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)

Rate of leaching increases with increasing

Flights in a rotary dryer are provided to

In most of the vacuum crystalliser, vacuum is generally produced by means of a

Coffee is prepared from coffee beans by leaching with

Minimum reflux ratio in a distillation column results in

Water entrained by circulating air in cooling towers is termed as

Dew point of an air-water vapor mixture

__________ developed the film theory.