A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture?

The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10.

The mixture exhibits an azeotrope at 101.3 kPa.

The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10.

The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10.

The mixture contain optical isomers.

Unsaturated air (with dry bulb and wet bulb temperatures being 45¬∞C and 25¬∞C respectively) is passed through a water spray chamber maintained at 23¬∞C. The air will be cooled and$

humidified at constant wet bulb temperature.

humidified with wet bulb temperature decreasing.

humidified at constant wet bulb temperature.

For water-ethanol system, the minimum reflux ratio

is computed from the intercept of the operating line.

is computed from the slope of the upper operating line that is tangent to the equilibrium curve.

is computed from the intercept of the operating line.

The expression, ln(F/W) = is

for NtoG in absorption for dilute mixture

differential distillation equation

for NtoG in absorption for dilute mixture

slope of q-line in McCabe-Thiele method

In extractive distillation, solvent is

added to alter the relative volatility of the mixture.

of high viscosity to give high tray efficiency.

The solvent used in liquid extraction should not have high latent heat of vaporisation, because

it will decompose while recovering by distillation.

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

it cannot be recovered by distillation.

its recovery cost by distillation may be prohibitatively high.

it will decompose while recovering by distillation.

The wetted wall tower is used to determine

M.T.C. of individual components in a liquid-liquid system.

individual mass transfer co-efficient (M.T.C.) in gaseous system.

M.T.C. of individual components in a liquid-liquid system.

M.T.C. of liquid in liquid-gas system.

the overall M.T.C. of the system.

Reboiler is considered as one theoretical plate, because

vapour is recycled to the column.

of the assumption that vapour and liquid leaving the reboiler are in equilibrium.

vapour is recycled to the column.

reboiler itself contains one plate.

Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the

high evaporation losses of water.

To get high tray efficiency

time of contact between the two phases should be less.

interfacial surface between liquid and gas phase should be large.

time of contact between the two phases should be less.

gas velocity should be very low.

liquid entrainment should be severe.

Absorption factor method is used to calculate the number of ideal stages, when

pressure drop in the column is very high.

operating line lies above the equilibrium line.

operating line lies below the equilibrium line.

both operating and equilibrium lines are parallel.

pressure drop in the column is very high.

In case of an absorber, the operating

line always lies below the equilibrium curve.

line always lies above the equilibrium curve.

line always lies below the equilibrium curve.

line can be either above or below the equilibrium curve.

velocity is more than the loading velocity.

For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.

major decrease in the number of

marginal decrease in the number of

major decrease in the number of

Dew point of a gas-vapour mixture

increases with increase in pressure.

increases with temperature rise.

decreases with temperature rise.

decreases with decrease in pressure.

increases with increase in pressure.

854 + Mcqs in Mass Transfer Page 13 McqOptions

601.	A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture?
A.	The mixture exhibits an azeotrope at 101.3 kPa.
B.	The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10.
C.	The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10.
D.	The mixture contain optical isomers.
Answer» B. The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and m-xylene 10.

Discussion

602.	The ratio of Murphree plate efficiency to point efficiency is 1 in a __________ flow model.
A.	plug
B.	perfectly mixed
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» C. both (a) & (b)

Discussion

603.	Gaseous diffusion co-efficient increases with increase in the
A.	pressure
B.	temperature
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» C. both (a) & (b)

Discussion

604.	Unsaturated air (with dry bulb and wet bulb temperatures being 45¬∞C and 25¬∞C respectively) is passed through a water spray chamber maintained at 23¬∞C. The air will be cooled and$
A.	humidified with wet bulb temperature decreasing.
B.	humidified at constant wet bulb temperature.
C.	dehumidified.
D.	none of these
Answer» B. humidified at constant wet bulb temperature.

Discussion

605.	For water-ethanol system, the minimum reflux ratio
A.	is computed from the slope of the upper operating line that is tangent to the equilibrium curve.
B.	is computed from the intercept of the operating line.
C.	cannot be computed.
D.	is the optimum reflux ratio.
Answer» B. is computed from the intercept of the operating line.

Discussion

606.	Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele's method ?
A.	Partial condenser
B.	Total condenser
C.	Reboiler
D.	Both (b) and (c)
Answer» E.

Discussion

607.	In gas-liquid contact operation, the number of ideal stages, . This is true when the stripping factor 'S' is
A.	S > 1
B.	S < 1
C.	S = 1
D.	S = ‚àû
Answer» B. S < 1

Discussion

608.	The process employing desorption of the absorbed solute by a solvent is called
A.	elution
B.	osmosis
C.	reverse osmosis
D.	sublimation
Answer» B. osmosis

Discussion

609.	Penetration model (theory) for mass transfer was enunciated by
A.	Danckwerts
B.	Toor and Marchello
C.	Higbie
D.	Kissinevskii
Answer» D. Kissinevskii

Discussion

610.	Cox chart is useful in the design of
A.	distillation column
B.	evaporator
C.	dryer
D.	crystalliser
Answer» B. evaporator

Discussion

611.	A mixture of 10% C6H6 vapour in air at 25¬∞C and 750 mm Hg has a dew point of 20¬∞C. Its dew point at 30¬∞C and 700 mm Hg will be around __________ ¬∞C.$
A.	21.7
B.	20
C.	27.3
D.	18.7
Answer» E.

Discussion

612.	The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is
A.	2
B.	0.5
C.	50
D.	150
Answer» B. 0.5

Discussion

613.	The expression, ln(F/W) = is
A.	differential distillation equation
B.	for NtoG in absorption for dilute mixture
C.	slope of q-line in McCabe-Thiele method
D.	for relative volatility
Answer» B. for NtoG in absorption for dilute mixture

Discussion

614.	With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas
A.	increases
B.	decreases
C.	decreases linearly
D.	remains unaffected
Answer» C. decreases linearly

Discussion

615.	The rough value of diffusion co-efficient of water vapor into air at 25¬∞C may be about __________ cm2/sec.$
A.	0.25
B.	2.5
C.	1.25
D.	0.0025
Answer» B. 2.5

Discussion

616.	For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around
A.	0.6
B.	0.24
C.	1
D.	0.72
Answer» D. 0.72

Discussion

617.	In extractive distillation, solvent is
A.	added to alter the relative volatility of the mixture.
B.	of high volatility.
C.	present in overhead stream.
D.	of high viscosity to give high tray efficiency.
Answer» B. of high volatility.

Discussion

618.	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 )
A.	T
B.	T
C.	T1.5
D.	T3
Answer» C. T1.5

Discussion

619.	The solvent used in liquid extraction should not have high latent heat of vaporisation, because
A.	the pressure drop and hence the pumping cost will be very high.
B.	it cannot be recovered by distillation.
C.	its recovery cost by distillation may be prohibitatively high.
D.	it will decompose while recovering by distillation.
Answer» D. it will decompose while recovering by distillation.

Discussion

620.	In case of gases, the binary diffusivity is proportional to (where, P = pressure)
A.	P
B.	1/P
C.	1/P
D.	P
Answer» C. 1/P

Discussion

621.	Ordinary diffusion process is also called __________ diffusion.
A.	pressure
B.	thermal
C.	concentration
D.	forced.
Answer» D. forced.

Discussion

622.	Desirable value of absorption factor in an absorber is
A.	1
B.	< 1
C.	> 1
D.	0.5
Answer» D. 0.5

Discussion

623.	Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes ?
A.	Packed towers
B.	Plate towers
C.	Spray towers
D.	Wetted wall columns
Answer» E.

Discussion

624.	The adiabatic saturation curve for a vapour-gas mixture is
A.	straight line.
B.	slightly concave upward.
C.	slightly concave downward.
D.	none of these.
Answer» C. slightly concave downward.

Discussion

625.	Design calculation for multiple component distillation is done by
A.	Ponchon-Savarit method
B.	Mccabe-Thiele method
C.	enthalpy concentration method
D.	tray to tray calculations.
Answer» E.

Discussion

626.	A 25 cm x 25 cm x 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m x 1m x 1cm flat sheet of the same material is to be dried from one side only.Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is
A.	1000
B.	1500
C.	2000
D.	2500
Answer» B. 1500

Discussion

627.	The wetted wall tower is used to determine
A.	individual mass transfer co-efficient (M.T.C.) in gaseous system.
B.	M.T.C. of individual components in a liquid-liquid system.
C.	M.T.C. of liquid in liquid-gas system.
D.	the overall M.T.C. of the system.
Answer» B. M.T.C. of individual components in a liquid-liquid system.

Discussion

628.	With increase in temperature, the leaching rate increases because of the
A.	increased diffusivity.
B.	decreased viscosity of liquid.
C.	both (a) and (b).
D.	neither (a) nor (b).
Answer» D. neither (a) nor (b).

Discussion

629.	Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.
A.	rotary
B.	tray
C.	freeze
D.	none of these
Answer» C. freeze

Discussion

630.	Reboiler is considered as one theoretical plate, because
A.	of the assumption that vapour and liquid leaving the reboiler are in equilibrium.
B.	vapour is recycled to the column.
C.	reboiler itself contains one plate.
D.	none of these.
Answer» B. vapour is recycled to the column.

Discussion

631.	Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant
A.	humidity
B.	velocity
C.	temperature
D.	all (a), (b) & (c)
Answer» E.

Discussion

632.	A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is
A.	0.54
B.	1.04
C.	1.24
D.	1.94
Answer» D. 1.94

Discussion

633.	Large scale drying of sugar is done in a __________ dryer.
A.	spouted bed
B.	tray
C.	rotary
D.	truck
Answer» D. truck

Discussion

634.	Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysterisis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption.
A.	lower than
B.	higher than
C.	same as
D.	either same or higher than
Answer» B. higher than

Discussion

635.	Which of the following provides maximum contact surface for a liquid-vapour system?
A.	Packed tower
B.	Bubble-cap plate column
C.	Seive-plate column
D.	Wetted wall column
Answer» B. Bubble-cap plate column

Discussion

636.	When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation.
A.	continuous
B.	steam
C.	azerotropic
D.	none of these
Answer» C. azerotropic

Discussion

637.	Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the
A.	high evaporation losses of water.
B.	high pressure drop of the gas.
C.	difficulty in its fabrication.
D.	none of these.
Answer» C. difficulty in its fabrication.

Discussion

638.	The relative humidity of air decreases in-spite of an increase in the absolute humidity, when the
A.	temperature rises.
B.	pressure rises.
C.	temperature falls.
D.	pressure falls.
Answer» B. pressure rises.

Discussion

639.	Diameter of raschig rings used in packed tower in industry is normally around __________ inches.
A.	2
B.	8
C.	12
D.	18
Answer» B. 8

Discussion

640.	Nitrobenzene (boiling point = 210.6¬∞C) is steam distilled at 1 atm pressure.Nitrobenzene will distill off __________ ¬∞C.$
A.	at < 100
B.	at > 210.6
C.	between 100 and 210
D.	none of these
Answer» B. at > 210.6

Discussion

641.	To get high tray efficiency
A.	interfacial surface between liquid and gas phase should be large.
B.	time of contact between the two phases should be less.
C.	gas velocity should be very low.
D.	liquid entrainment should be severe.
Answer» B. time of contact between the two phases should be less.

Discussion

642.	In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number.
A.	Lewis
B.	Grashoff
C.	Sherwood
D.	none of these
Answer» B. Grashoff

Discussion

643.	Dry bulb temperature of the gas is __________ the wet bulb temperature.
A.	less than
B.	more than
C.	equal to
D.	none of these
Answer» C. equal to

Discussion

644.	Raoult's law applies to the
A.	all liquid solutions
B.	non-ideal solution only.
C.	non-volatile solute.
D.	solvents.
Answer» E.

Discussion

645.	Absorption factor method is used to calculate the number of ideal stages, when
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.
Answer» D. pressure drop in the column is very high.

Discussion

646.	In case of an absorber, the operating
A.	line always lies above the equilibrium curve.
B.	line always lies below the equilibrium curve.
C.	line can be either above or below the equilibrium curve.
D.	velocity is more than the loading velocity.
Answer» B. line always lies below the equilibrium curve.

Discussion

647.	For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.
A.	no change in theoretical
B.	marginal decrease in the number of
C.	major decrease in the number of
D.	none of these
Answer» C. major decrease in the number of

Discussion

648.	Dew point of a gas-vapour mixture
A.	increases with temperature rise.
B.	decreases with temperature rise.
C.	decreases with decrease in pressure.
D.	increases with increase in pressure.
Answer» D. increases with increase in pressure.

Discussion

649.	Pore size of the molecular seive 5A is __________ mm.
A.	5
B.	0.5
C.	0.05
D.	50
Answer» C. 0.05

Discussion

650.	For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams
A.	increases
B.	decreases
C.	remains unaffected
D.	passes through a maximum
Answer» B. decreases

Discussion

Explore topic-wise MCQs in Chemical Engineering.

A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture?

The ratio of Murphree plate efficiency to point efficiency is 1 in a __________ flow model.

Gaseous diffusion co-efficient increases with increase in the

Unsaturated air (with dry bulb and wet bulb temperatures being 45¬∞C and 25¬∞C respectively) is passed through a water spray chamber maintained at 23¬∞C. The air will be cooled and$

For water-ethanol system, the minimum reflux ratio

Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele's method ?

In gas-liquid contact operation, the number of ideal stages, . This is true when the stripping factor 'S' is

The process employing desorption of the absorbed solute by a solvent is called

Penetration model (theory) for mass transfer was enunciated by

Cox chart is useful in the design of

A mixture of 10% C6H6 vapour in air at 25¬∞C and 750 mm Hg has a dew point of 20¬∞C. Its dew point at 30¬∞C and 700 mm Hg will be around __________ ¬∞C.$

The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is

The expression, ln(F/W) = is

With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas

The rough value of diffusion co-efficient of water vapor into air at 25¬∞C may be about __________ cm2/sec.$

For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around

In extractive distillation, solvent is

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 )

The solvent used in liquid extraction should not have high latent heat of vaporisation, because

In case of gases, the binary diffusivity is proportional to (where, P = pressure)

Ordinary diffusion process is also called __________ diffusion.

Desirable value of absorption factor in an absorber is

Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes ?

The adiabatic saturation curve for a vapour-gas mixture is

Design calculation for multiple component distillation is done by

The wetted wall tower is used to determine

With increase in temperature, the leaching rate increases because of the

Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.

Reboiler is considered as one theoretical plate, because

Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is

Large scale drying of sugar is done in a __________ dryer.

Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysterisis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption.

Which of the following provides maximum contact surface for a liquid-vapour system?

When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation.

Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the

The relative humidity of air decreases in-spite of an increase in the absolute humidity, when the

Diameter of raschig rings used in packed tower in industry is normally around __________ inches.

Nitrobenzene (boiling point = 210.6¬∞C) is steam distilled at 1 atm pressure.Nitrobenzene will distill off __________ ¬∞C.$

To get high tray efficiency

In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number.

Dry bulb temperature of the gas is __________ the wet bulb temperature.

Raoult's law applies to the

Absorption factor method is used to calculate the number of ideal stages, when

In case of an absorber, the operating

For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.

Dew point of a gas-vapour mixture

Pore size of the molecular seive 5A is __________ mm.

For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams