Which of these columns incurs the lowest pressure drop?

Packed column (with dumped packing)

Packed column (with stacked packing)

Packed column (with dumped packing)

Can a cooling tower cool water below the wet bulb temperature of inlet air?

Yes ; but height of cooling tower will be prohibitively high

Yes ; but the air flow rate should be excessively high

Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled

And dehumidified with increase in wet bulb temperature

And dehumidified with decrease in wet bulb temperature

Which of the following unit operations makes use of Thiele-Geddes equation?

Multicomponent absorption with chemical reaction

For an absorber, both equilibrium and operating line will be straight for

concentrated solution and isothermal operation.

concentrated solution and non-isothermal operation.

dilute solution and non-isothermal operation.

dilute solution and isothermal operation.

concentrated solution and isothermal operation.

Pick out the wrong statement pertaining to leaching.

Door classifier can be used for leaching of coarse solids.

Fine solids can not be leached in a Pachuka tank.

Door classifier can be used for leaching of coarse solids.

Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor.

Very high temperature is not needed for the leaching of sugar beet.

In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is

equal to the heat of formation of surface compound.

called integral heat of adsorption.

In case of absorption with exothermic reaction, for fluids having

Pr = Sc ; there won't be any change in heat and mass transfer flux with changes in degree of turbulence.

Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence.

Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same.

Pr = Sc ; there won't be any change in heat and mass transfer flux with changes in degree of turbulence.

In rectifying section of a continuous distillation column, the

liquid is stripped of high boilers.

vapour is enriched with low boilers.

vapour is enriched with high boilers.

liquid is stripped of high boilers.

Flash distillation is suitable for separating the constituents of a binary system, which

have very close boiling points.

form minimum boiling azeotrope.

have very close boiling points.

form constant boiling azeotrope.

An ideal tower packing should not

have low weight per unit volume.

have large surface area per unit volume.

hold up large amount of liquid in the packing.

In a distillation column, with increase in the reflux ratio, the heat removed in the cooler

and the heat required in reboiler decreases.

Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent ?

Dehumidification with dry bulb temperature remaining constant.

Heating and dehumidification at almost constant wet bulb temperature.

Dehumidification with dry bulb temperature remaining constant.

If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that

the system comprises of partially mis-cible liquids.

the system comprises of miscible liquids.

the system comprises of an azeotrope.

on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.

854 + Mcqs in Mass Transfer in Chemical Engineering Page 5 McqOptions

201.	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

202.	Deairation (removal of O₂) of water is done by
A.	Rectification
B.	Absorption
C.	Ion-exchange
D.	Adsorption
Answer» D. Adsorption

Discussion

203.	Which of these columns incurs the lowest pressure drop?
A.	Packed column (with stacked packing)
B.	Packed column (with dumped packing)
C.	Bubble plate column
D.	Pulse column
Answer» B. Packed column (with dumped packing)

Discussion

204.	Can a cooling tower cool water below the wet bulb temperature of inlet air?
A.	Yes
B.	No
C.	Yes ; but height of cooling tower will be prohibitively high
D.	Yes ; but the air flow rate should be excessively high
Answer» C. Yes ; but height of cooling tower will be prohibitively high

Discussion

205.	Pick out the correct relationship. (where, Ri = internal reflux ratio Ro = external reflux ratio. )
A.	(1 + Ro) = Ro/Ri
B.	(1 - Ro) = Ro/Ri
C.	(1 + Ri) = Ro/Ri
D.	(1 - Ri) = Ro/Ri
Answer» B. (1 - Ro) = Ro/Ri

Discussion

206.	In which of the following unit operations, the selectivity is an important parameter?
A.	Distillation
B.	Solvent extraction
C.	Absorption
D.	None of these
Answer» C. Absorption

Discussion

207.	A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)
A.	M(Xo - XF)
B.	M(Xo/XF)
C.	M ln(Xo/XF)
D.	MXo ln(Xo/XF)
Answer» E.

Discussion

208.	(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

209.	The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.)
A.	Kc = Kp = Km
B.	Kc = Kp/RT = Km . RT/P
C.	Kc = Kp . RT = Km . RT/p
D.	None of these
Answer» D. None of these

Discussion

210.	Which of the following equipments is not used for liquid dispersion?
A.	Wetted wall towers
B.	Packed towers
C.	Venturi scrubbers
D.	Agitated vessels
Answer» E.

Discussion

211.	Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled
A.	And humidified
B.	And dehumidified with increase in wet bulb temperature
C.	At the same relative humidity
D.	And dehumidified with decrease in wet bulb temperature
Answer» E.

Discussion

212.	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

213.	The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and, m = slope of the equilibrium line)
A.	L/mG
B.	G/mL
C.	ML/G
D.	LG/m
Answer» B. G/mL

Discussion

214.	At what value of reflux ratio, number of theoretical plates in a distillation column is minimum?
A.	0
B.	1
C.	∞
D.	< 1
Answer» D. < 1

Discussion

215.	Which of the following equipments is not used for gas dispersion?
A.	Agitated vessels
B.	Bubble cap tray towers
C.	Perforated sieve tray towers
D.	Spray towers
Answer» E.

Discussion

216.	Which of the following unit operations makes use of Thiele-Geddes equation?
A.	Liquid-liquid extraction
B.	Solid-liquid extraction
C.	Multicomponent absorption with chemical reaction
D.	Multicomponent distillation
Answer» E.

Discussion

217.	H₂S present in naphtha reformed gas is removed by absorbing with
A.	Ethanolamine
B.	K₂CO₃
C.	HCl
D.	Vacuum gas oil
Answer» B. K₂CO₃

Discussion

218.	In paper industry, paper is dried in a __________ dryer.
A.	Tunnel
B.	Heated cylinder
C.	Conveyor
D.	Festoon
Answer» C. Conveyor

Discussion

219.	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/πt)1/2
D.	(4De/t)
Answer» D. (4De/t)

Discussion

220.	Which of the following is an undesirable property for an absorbing solvent?
A.	Low vapour pressure
B.	Low velocity
C.	Low freezing point
D.	None of these
Answer» E.

Discussion

221.	JD factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by
A.	Nsh = 2
B.	Nst = 2
C.	Nsc = 2
D.	None of these
Answer» B. Nst = 2

Discussion

222.	The value of NA/(NA + NB) for steady state molecular diffusion of gas 'A' through non-diffusing gas 'B' is
A.	1
B.	∞
C.	0.5
D.	2
Answer» B. ∞

Discussion

223.	Which of the following same diameter columns gives lowest pressure drop per unit height?
A.	Bubble-cap column
B.	Sieve-plate column
C.	Packed column (stacked)
D.	Randomly packed column
Answer» D. Randomly packed column

Discussion

224.	The diffusivity (D) in a binary gas mixture is related to the pressure (P) as
A.	D ∝ P0.5
B.	D ∝ 1/P0.5
C.	D ∝ 1/P
D.	D ∝ 1/P1.5
Answer» D. D ∝ 1/P1.5

Discussion

225.	What is the reflux ratio at total reflux?
A.	Zero
B.	Infinity
C.	Unity
D.	Data insufficient
Answer» C. Unity

Discussion

226.	Gaseous diffusivity at atmospheric pressure is of the order of __________ cm²/second.
A.	1
B.	1 to 5
C.	5 to 10
D.	> 10
Answer» B. 1 to 5

Discussion

227.	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

228.	The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________
A.	1
B.	0.5
C.	10
D.	0
Answer» B. 0.5

Discussion

229.	The dimension of diffusivity is same as that of the
A.	density
B.	molal concentration
C.	kinematic viscosity
D.	velocity head
Answer» D. velocity head

Discussion

230.	For an absorber, both equilibrium and operating line will be straight for
A.	concentrated solution and non-isothermal operation.
B.	dilute solution and non-isothermal operation.
C.	dilute solution and isothermal operation.
D.	concentrated solution and isothermal operation.
Answer» D. concentrated solution and isothermal operation.

Discussion

231.	Pick out the wrong statement pertaining to leaching.
A.	Fine solids can not be leached in a Pachuka tank.
B.	Door classifier can be used for leaching of coarse solids.
C.	Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor.
D.	Very high temperature is not needed for the leaching of sugar beet.
Answer» B. Door classifier can be used for leaching of coarse solids.

Discussion

232.	In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is
A.	equal to the heat of formation of surface compound.
B.	equal to the heat of wetting.
C.	zero.
D.	called integral heat of adsorption.
Answer» C. zero.

Discussion

233.	If the amount of the steam used in steam distillation is increased, the temperature of distillation
A.	increases
B.	decreases
C.	remains unchanged
D.	depends on relative volatility
Answer» C. remains unchanged

Discussion

234.	Cox chart, which is useful in the design of distillation column particularly for petroleum hydrocarbons, is a plot of (where, P = vapor pressure, T = temperature)
A.	log P vs . T
B.	log P vs. log T
C.	T vs . P
D.	P vs . log T
Answer» B. log P vs. log T

Discussion

235.	Packed column distillation is limited to the column __________ metres.
A.	height < 6
B.	diameter < 0.6
C.	both (a) & (b)
D.	neither (a) nor (b).
Answer» D. neither (a) nor (b).

Discussion

236.	In case of absorption with exothermic reaction, for fluids having
A.	Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence.
B.	Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same.
C.	both (a) and (b)
D.	Pr = Sc ; there won't be any change in heat and mass transfer flux with changes in degree of turbulence.
Answer» D. Pr = Sc ; there won't be any change in heat and mass transfer flux with changes in degree of turbulence.

Discussion

237.	Water-ethyl alcohal solution can be concentrated (in respect of alcohal concentration) by __________ distillation.
A.	atmospheric
B.	vacuum
C.	high pressure
D.	none of these
Answer» C. high pressure

Discussion

238.	In rectifying section of a continuous distillation column, the
A.	vapour is enriched with low boilers.
B.	vapour is enriched with high boilers.
C.	liquid is stripped of high boilers.
D.	none of these.
Answer» C. liquid is stripped of high boilers.

Discussion

239.	A binary mixture of benzene and cyclohexane is separated by
A.	flash vaporisation
B.	extractive distillation
C.	solvent extraction
D.	ordinary distillation
Answer» C. solvent extraction

Discussion

240.	Flash distillation is suitable for separating the constituents of a binary system, which
A.	form minimum boiling azeotrope.
B.	have very wide boiling points.
C.	have very close boiling points.
D.	form constant boiling azeotrope.
Answer» C. have very close boiling points.

Discussion

241.	With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature)
A.	increases
B.	remains unchanged
C.	decreases
D.	decreases linearly
Answer» B. remains unchanged

Discussion

242.	In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated.
A.	molecular
B.	azeotropic
C.	extractive
D.	flash.
Answer» D. flash.

Discussion

243.	An ideal tower packing should not
A.	have low weight per unit volume.
B.	have large surface area per unit volume.
C.	have large free cross-section.
D.	hold up large amount of liquid in the packing.
Answer» E.

Discussion

244.	In a distillation column, with increase in the reflux ratio, the heat removed in the cooler
A.	increases.
B.	decreases.
C.	remains unaffected.
D.	and the heat required in reboiler decreases.
Answer» B. decreases.

Discussion

245.	The minimum number of theoretical plates is required for achieving a given separation in distillation column with
A.	no reflux
B.	total reflux
C.	zero reflux ratio
D.	minimum reflux ratio
Answer» C. zero reflux ratio

Discussion

246.	Steady state equimolal counter diffusion occurs in case of
A.	leaching
B.	absorption
C.	binary phase distillation
D.	liquid-liquid extraction
Answer» D. liquid-liquid extraction

Discussion

247.	Dry bulb temperature of unsaturated air is more than its __________ temperature.
A.	dew point
B.	wet bulb
C.	both 'a' & 'b'
D.	neither 'a' nor 'b'
Answer» D. neither 'a' nor 'b'

Discussion

248.	Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent ?
A.	Cooling and dehumidification.
B.	Heating and dehumidification at almost constant wet bulb temperature.
C.	Dehumidification with dry bulb temperature remaining constant.
D.	None of these.
Answer» C. Dehumidification with dry bulb temperature remaining constant.

Discussion

249.	If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that
A.	the system comprises of partially mis-cible liquids.
B.	the system comprises of miscible liquids.
C.	the system comprises of an azeotrope.
D.	on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.
Answer» E.

Discussion

250.	In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at __________ reflux.
A.	total
B.	minimum
C.	operating
D.	maximum permissible
Answer» B. minimum

Discussion

Explore topic-wise MCQs in Chemical Engineering.

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

Deairation (removal of O₂) of water is done by

Which of these columns incurs the lowest pressure drop?

Can a cooling tower cool water below the wet bulb temperature of inlet air?

Pick out the correct relationship. (where, Ri = internal reflux ratio Ro = external reflux ratio. )

In which of the following unit operations, the selectivity is an important parameter?

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

Which of the following equipments is not used for liquid dispersion?

Unsaturated air (with dry bulb temperature and dew point being 35°C and 18°C respectively) is passed through a water spray chamber maintained at 15°C. The air will be cooled

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

The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and, m = slope of the equilibrium line)

At what value of reflux ratio, number of theoretical plates in a distillation column is minimum?

Which of the following equipments is not used for gas dispersion?

Which of the following unit operations makes use of Thiele-Geddes equation?

H₂S present in naphtha reformed gas is removed by absorbing with

In paper industry, paper is dried in a __________ dryer.

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

Which of the following is an undesirable property for an absorbing solvent?

JD factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by

The value of NA/(NA + NB) for steady state molecular diffusion of gas 'A' through non-diffusing gas 'B' is

Which of the following same diameter columns gives lowest pressure drop per unit height?

The diffusivity (D) in a binary gas mixture is related to the pressure (P) as

What is the reflux ratio at total reflux?

Gaseous diffusivity at atmospheric pressure is of the order of __________ cm²/second.

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)

The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________

The dimension of diffusivity is same as that of the

For an absorber, both equilibrium and operating line will be straight for

Pick out the wrong statement pertaining to leaching.

In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is

If the amount of the steam used in steam distillation is increased, the temperature of distillation

Cox chart, which is useful in the design of distillation column particularly for petroleum hydrocarbons, is a plot of (where, P = vapor pressure, T = temperature)

Packed column distillation is limited to the column __________ metres.

In case of absorption with exothermic reaction, for fluids having

Water-ethyl alcohal solution can be concentrated (in respect of alcohal concentration) by __________ distillation.

In rectifying section of a continuous distillation column, the

A binary mixture of benzene and cyclohexane is separated by

Flash distillation is suitable for separating the constituents of a binary system, which

With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature)

In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated.

An ideal tower packing should not

In a distillation column, with increase in the reflux ratio, the heat removed in the cooler

The minimum number of theoretical plates is required for achieving a given separation in distillation column with

Steady state equimolal counter diffusion occurs in case of

Dry bulb temperature of unsaturated air is more than its __________ temperature.

Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent ?

In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at __________ reflux.