The falling rate period in the drying of a solid is characterised by

increasing temperatures both on the surface and within the solid.

In an operating distillation column, the

highest temperature is encountered at the top of the column.

vapors and liquids are at their dew point and bubble point respectively

driving force for the liquid flow is its specific weight.

driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.

highest temperature is encountered at the top of the column.

In a counter-current extractor, as the axial mixing increases, the extraction efficiency

depends on the pressure of the system

HETP is numerically equal to HTU, only when the operating line

is far from the equilibrium line.

lies below the equilibrium line.

lies above the equilibrium line.

and equilibrium lines are parallel.

is far from the equilibrium line.

With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux

may increase or decrease ; depends on system.

An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)

composition of the residue remains unchanged.

less number of trays are required.

composition of the residue remains unchanged.

more number of trays are required but the residue composition remains unchanged.

more number of trays are required and the residue composition is more dilute in methanol.

The humid volume may be increased by increasing the

temperature at constant humidity.

humidity at constant temperature.

Ponchan-Savarit method analyses the fractional equipment based on

the assumption of constant molaloverflow.

both enthalpy and material balances.

the assumption of constant molaloverflow.

When an unsaturated air-water mixture is heated at constant pressure, then

the partial pressure of water vapour increases.

the specific humidity decreases.

The relative humidity increases.

the relative humidity decreases.

Pick out the wrong statement pertaining to the cooling towers.

In case of induced draft cooling tower, the fan is placed at the top of the tower.

Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air.

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

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

The 'shanks system' of leaching (i.e., counter-current multiple contact leaching) is used for

recovery of tannis from the tree barks and woods.

leaching sodium nitrate from Chilean nitrate bearing rock.

In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when

the latent heat of vaporisation of the more and less volatile components are greatly different.

Steam distillation is used to separate

high boiling substances from nonvolatile impurities.

mixtures of low relative volatility.

The main reason for dividing a tall packed tower into series of small towers is to

minimise the overall pressure drop.

Chemisorption compared to physical absorption has

lower capacity of the solvent for the solute gas.

increased utilisation of stagnant zones of the liquid phase.

'Absorption with chemical reaction' is involved in the removal of

benzol from coke oven gas using solar oil/wash oil.

carbon dioxide from gaseous stream using alkaline solution.

benzol from coke oven gas using solar oil/wash oil.

ammonia from coke oven gas using refrigerated water.

tar from coke oven gas in primary gas coolers using chilled water.

The term "approach" in a cooling tower refers to the difference in the temperature of the

hot water entering the tower and the wet bulb temperature of the surrounding air.

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

hot water entering the tower and the wet bulb temperature of the surrounding air.

hot water entering and the cooled water leaving the cooling tower.

Batch tray dryers suffers from the disadvantage of

non-uniform & low production rate.

high labour cost & low heat economy.

Priming in a distillation column

reduces the overall pressure drop.

results from very low gas velocity.

is desirable from point efficiency consideration.

is characterised by the presence of foam throughout the space between trays.

reduces the overall pressure drop.

Which of the following employs an accessory known as 'drift eliminator' ?

Mechanical draft cooling tower.

Capacity of a rotary dryer depends on its

inclination with ground surface

During the constant rate period of drying of a solid,

increased air humidity decreases the rate of drying.

increasing the air temperature decreases the drying rate.

surface evaporation of unbound moisture occurs.

As the reflux ratio increases, the slope of the operating line for rectifying section

data insufficient, cannot be predicted

854 + Mcqs in Mass Transfer in Chemical Engineering Page 7 McqOptions

301.	Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be
A.	1
B.	> 1
C.	< 1
D.	‚â§ 1
Answer» C. < 1

Discussion

302.	Drying of refractory is normally carried out in a __________ dryer.
A.	open pan
B.	tray
C.	rotary vacuum
D.	truck/tunnel.
Answer» E.

Discussion

303.	The unit of volumetric diffusivity is
A.	cm2/sec
B.	cm/sec
C.	cm3/sec
D.	cm2/sec2
Answer» B. cm/sec

Discussion

304.	The falling rate period in the drying of a solid is characterised by
A.	increase in rate of drying.
B.	increasing temperatures both on the surface and within the solid.
C.	decreasing temperatures.
D.	none of these.
Answer» C. decreasing temperatures.

Discussion

305.	The drying time between fixed moisture content within diffusion controlled 'falling 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.	T2
D.	T3
Answer» D. T3

Discussion

306.	In an operating distillation column, the
A.	vapors and liquids are at their dew point and bubble point respectively
B.	driving force for the liquid flow is its specific weight.
C.	driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.
D.	highest temperature is encountered at the top of the column.
Answer» D. highest temperature is encountered at the top of the column.

Discussion

307.	In a counter-current extractor, as the axial mixing increases, the extraction efficiency
A.	increases
B.	decreases
C.	remains unchanged
D.	depends on the pressure of the system
Answer» C. remains unchanged

Discussion

308.	The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases 'A' and 'B' is
A.	1
B.	‚àû
C.	0.5
D.	2
Answer» C. 0.5

Discussion

309.	HETP is numerically equal to HTU, only when the operating line
A.	lies below the equilibrium line.
B.	lies above the equilibrium line.
C.	and equilibrium lines are parallel.
D.	is far from the equilibrium line.
Answer» D. is far from the equilibrium line.

Discussion

310.	Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture.
A.	free
B.	unbound
C.	equilibrium
D.	bound
Answer» D. bound

Discussion

311.	Channelling in a packed tower results from the
A.	high pressure drop
B.	maldistribution of liquid
C.	non-uniformity of packing
D.	both (b) and (c)
Answer» E.

Discussion

312.	With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux
A.	increases
B.	decreases
C.	remains same
D.	may increase or decrease ; depends on system.
Answer» C. remains same

Discussion

313.	An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)
A.	less number of trays are required.
B.	composition of the residue remains unchanged.
C.	more number of trays are required but the residue composition remains unchanged.
D.	more number of trays are required and the residue composition is more dilute in methanol.
Answer» B. composition of the residue remains unchanged.

Discussion

314.	The critical moisture content in case of drying indicates the __________ rate period.
A.	beginning of falling
B.	beginning of constant
C.	end of falling
D.	none of these
Answer» B. beginning of constant

Discussion

315.	The humid volume may be increased by increasing the
A.	temperature at constant humidity.
B.	humidity at constant temperature.
C.	both (a) and (b).
D.	neither (a) nor (b).
Answer» D. neither (a) nor (b).

Discussion

316.	Ponchan-Savarit method analyses the fractional equipment based on
A.	enthalpy balance only.
B.	material balance only.
C.	both enthalpy and material balances.
D.	the assumption of constant molaloverflow.
Answer» D. the assumption of constant molaloverflow.

Discussion

317.	When an unsaturated air-water mixture is heated at constant pressure, then
A.	the partial pressure of water vapour increases.
B.	the specific humidity decreases.
C.	The relative humidity increases.
D.	the relative humidity decreases.
Answer» E.

Discussion

318.	Pick out the wrong statement pertaining to the cooling towers.
A.	In case of induced draft cooling tower, the fan is placed at the top of the tower.
B.	Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air.
C.	A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low.
D.	Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.
Answer» E.

Discussion

319.	H2S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H2S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in metres) corresponding to an operating line given by, y = 5x + 0.001 is
A.	2
B.	1.56
C.	1
D.	0.56
Answer» B. 1.56

Discussion

320.	The 'shanks system' of leaching (i.e., counter-current multiple contact leaching) is used for
A.	recovery of tannis from the tree barks and woods.
B.	leaching sodium nitrate from Chilean nitrate bearing rock.
C.	both (a) and (b).
D.	neither (a) nor (b).
Answer» D. neither (a) nor (b).

Discussion

321.	The solvent used in liquid-liquid extraction should have __________ less than one.
A.	selectivity
B.	distribution co-efficient
C.	both (a) and (b)
D.	neither (a) nor (b).
Answer» E.

Discussion

322.	__________ is the separation technique used for desalination of sea water.
A.	Thermal diffusion
B.	Reverse osmosis
C.	Adsorption
D.	absorption
Answer» C. Adsorption

Discussion

323.	When the feed to a distillation column is a saturated liquid, slope of the feed line is
A.	zero
B.	unity
C.	infinity
D.	none of these
Answer» D. none of these

Discussion

324.	The efficiency of a plate column will be maximum, when the flow is ideal __________ the plate.
A.	across
B.	above
C.	both (a) & (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

325.	In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when
A.	saturated feed is not used.
B.	an azeotrope forms.
C.	the latent heat of vaporisation of the more and less volatile components are greatly different.
D.	a total condenser is used.
Answer» E.

Discussion

326.	Which of the following can be calculated theoretically using steam table and Dalton's law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known ?
A.	Dew point
B.	Humidity ratio
C.	Wet bulb temperature
D.	None of these
Answer» D. None of these

Discussion

327.	Steam distillation is used to separate
A.	azeotropes.
B.	high boiling substances from nonvolatile impurities.
C.	heat sensitive materials.
D.	mixtures of low relative volatility.
Answer» C. heat sensitive materials.

Discussion

328.	The main reason for dividing a tall packed tower into series of small towers is to
A.	minimise the overall pressure drop.
B.	avoid flooding.
C.	reduce liquid hold up.
D.	avoid channeling.
Answer» E.

Discussion

329.	Large scale usage of flash distillation is practised in
A.	soap manufacturing
B.	ammonia synthesis plant
C.	polymerisation industry
D.	petroleum refinning
Answer» E.

Discussion

330.	Chemisorption compared to physical absorption has
A.	lower adsorption rate.
B.	lower capacity of the solvent for the solute gas.
C.	increased utilisation of stagnant zones of the liquid phase.
D.	none of these.
Answer» D. none of these.

Discussion

331.	The-relative volatility for separation of a non-ideal binary mixture by distillation should be
A.	0
B.	1
C.	> 1
D.	< 1
Answer» D. < 1

Discussion

332.	'Absorption with chemical reaction' is involved in the removal of
A.	carbon dioxide from gaseous stream using alkaline solution.
B.	benzol from coke oven gas using solar oil/wash oil.
C.	ammonia from coke oven gas using refrigerated water.
D.	tar from coke oven gas in primary gas coolers using chilled water.
Answer» B. benzol from coke oven gas using solar oil/wash oil.

Discussion

333.	In triangular co-ordinates, the ternery composition point falls __________ of the triangle.
A.	in the corners
B.	inside
C.	on the sides
D.	none of these.
Answer» C. on the sides

Discussion

334.	The term "approach" in a cooling tower refers to the difference in the temperature of the
A.	cold water leaving the tower and the wet bulb temperature of the surrounding air.
B.	hot water entering the tower and the wet bulb temperature of the surrounding air.
C.	hot water entering and the cooled water leaving the cooling tower.
D.	none of these
Answer» B. hot water entering the tower and the wet bulb temperature of the surrounding air.

Discussion

335.	Raoult's law is applicable to the
A.	ideal solutions
B.	real solutions
C.	mixture of water and alcohol
D.	non-ideal gases
Answer» B. real solutions

Discussion

336.	A slurry is to be dried to produce flaky solid. Which dryer would you recommend ?
A.	Spray dryer
B.	Drum dryer
C.	Rotary dryer
D.	Dielectric dryer
Answer» B. Drum dryer

Discussion

337.	Batch tray dryers suffers from the disadvantage of
A.	high maintenance cost.
B.	non-uniform & low production rate.
C.	high labour cost & low heat economy.
D.	all 'a', 'b' & 'c'.
Answer» D. all 'a', 'b' & 'c'.

Discussion

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

Discussion

339.	Priming in a distillation column
A.	results from very low gas velocity.
B.	is desirable from point efficiency consideration.
C.	is characterised by the presence of foam throughout the space between trays.
D.	reduces the overall pressure drop.
Answer» D. reduces the overall pressure drop.

Discussion

340.	Which of the following employs an accessory known as 'drift eliminator' ?
A.	Multiple effect evaporator.
B.	Mechanical draft cooling tower.
C.	Rotary dryer.
D.	Rotating disc contactor.
Answer» C. Rotary dryer.

Discussion

341.	Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2. hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is
A.	0.25
B.	0.5
C.	0.7
D.	0.9
Answer» C. 0.7

Discussion

342.	Capacity of a rotary dryer depends on its
A.	r.p.m
B.	inclination with ground surface
C.	both (a) and (b)
D.	neither (a) nor (b)
Answer» D. neither (a) nor (b)

Discussion

343.	During the constant rate period of drying of a solid,
A.	increased air humidity decreases the rate of drying.
B.	increasing the air temperature decreases the drying rate.
C.	surface evaporation of unbound moisture occurs.
D.	none of these.
Answer» D. none of these.

Discussion

344.	As the reflux ratio increases, the slope of the operating line for rectifying section
A.	increases
B.	decreases
C.	remains constant
D.	data insufficient, cannot be predicted
Answer» B. decreases

Discussion

345.	Which of the following is used for the concentration of rubber latex ?
A.	Agitated film evaporator
B.	Long tube vertical evaporator
C.	Short tube evaporator
D.	Calendria
Answer» B. Long tube vertical evaporator

Discussion

346.	Equilibrium moisture of a solid is equal to the total moisture minus free moisture. Which of the following substances will have maxi-mum equilibrium moisture ?
A.	Anthracite coal
B.	Rag paper
C.	Bamboo
D.	Inorganic solids
Answer» D. Inorganic solids

Discussion

347.	Unit of molal diffusivity is
A.	cm2/sec gm . mole
B.	gm moles/cm2 . sec
C.	gm moles/cm. sec
D.	gm moles/cm2. sec
Answer» D. gm moles/cm2. sec

Discussion

348.	Rate of adsorption increases as the
A.	temperature increases.
B.	temperature decreases.
C.	pressure decreases.
D.	size of adsorbent increases.
Answer» C. pressure decreases.

Discussion

349.	Smoke is an example of
A.	solid dispersed in liquid
B.	solid dispersed in gas
C.	liquid dispersed in gas
D.	gas dispersed in liquid
Answer» C. liquid dispersed in gas

Discussion

350.	Which of the following has the same dimension as mass diffusivity ?
A.	Momentum flux
B.	Kinematic viscosity
C.	Thermal diffusivity
D.	Both (b) and (c)
Answer» E.

Discussion

Explore topic-wise MCQs in Chemical Engineering.

Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be

Drying of refractory is normally carried out in a __________ dryer.

The unit of volumetric diffusivity is

The falling rate period in the drying of a solid is characterised by

The drying time between fixed moisture content within diffusion controlled 'falling rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid )

In an operating distillation column, the

In a counter-current extractor, as the axial mixing increases, the extraction efficiency

The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases 'A' and 'B' is

HETP is numerically equal to HTU, only when the operating line

Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture.

Channelling in a packed tower results from the

With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux

The critical moisture content in case of drying indicates the __________ rate period.

The humid volume may be increased by increasing the

Ponchan-Savarit method analyses the fractional equipment based on

When an unsaturated air-water mixture is heated at constant pressure, then

Pick out the wrong statement pertaining to the cooling towers.

The 'shanks system' of leaching (i.e., counter-current multiple contact leaching) is used for

The solvent used in liquid-liquid extraction should have __________ less than one.

__________ is the separation technique used for desalination of sea water.

When the feed to a distillation column is a saturated liquid, slope of the feed line is

The efficiency of a plate column will be maximum, when the flow is ideal __________ the plate.

In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when

Which of the following can be calculated theoretically using steam table and Dalton's law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known ?

Steam distillation is used to separate

The main reason for dividing a tall packed tower into series of small towers is to

Large scale usage of flash distillation is practised in

Chemisorption compared to physical absorption has

The-relative volatility for separation of a non-ideal binary mixture by distillation should be

'Absorption with chemical reaction' is involved in the removal of

In triangular co-ordinates, the ternery composition point falls __________ of the triangle.

The term "approach" in a cooling tower refers to the difference in the temperature of the

Raoult's law is applicable to the

A slurry is to be dried to produce flaky solid. Which dryer would you recommend ?

Batch tray dryers suffers from the disadvantage of

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

Priming in a distillation column

Which of the following employs an accessory known as 'drift eliminator' ?

Capacity of a rotary dryer depends on its

During the constant rate period of drying of a solid,

As the reflux ratio increases, the slope of the operating line for rectifying section

Which of the following is used for the concentration of rubber latex ?

Equilibrium moisture of a solid is equal to the total moisture minus free moisture. Which of the following substances will have maxi-mum equilibrium moisture ?

Unit of molal diffusivity is

Rate of adsorption increases as the

Smoke is an example of

Which of the following has the same dimension as mass diffusivity ?