m tr Flashcards
Mass transfer rate between two fluid phases does not
necessarily depend on the __________ of the two phases.
A. chemical properties
B. physical properties
C. degree of turbulence
D. interfacial area
A
In a solution containing 0.30 Kg mole of solute and 600 kg of
solvent, the molality is
A. 0.50
B. 0.60
C. 2
D. 1
A
Fenske equation determines the
A. maximum number of ideal plates.
B. height of the distillation column.
C. minimum number of theoretical plates.
D. optimum reflux ratio.
C
The term “cooling range” in a cooling tower refers to the
difference in the temperature of
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 the tower and the cooled water
leaving the tower.
D. none of these
C
Which of the following is the most suitable for extraction in a
system having very low density difference?
A. Mixer-settler extractor
B. Centrifugal extractor
C. Pulsed extractor
D. Packed extraction tower
B
Total reflux in a distillation operation requires minimum
A. reboiler load.
B. number of plates
C. condenser load
D. all (a), (b) and (c)
B
As the reflux ratio in a distillation coloumn is increased from the
minimum, the
A. slope of the operating line in stripping section
decreases.
B. number of plates decreases very slowly first and then
more and more rapidly.
C. total cost first decreases and then increases.
D. liquid flow increases while the vapor flow decreases
for a system.
C
The amount of steam required per unit quantity of distillate in
case of steam distillation will be reduced by
A. raising the temperature.
B. lowering the total pressure.
C. both (a) and (b).
D. neither (a) nor (b).
C
Fenske’s equation for determining the minimum number of
theoretical stages in distillation column holds good, when the
A. relative volatility is reasonably constant.
B. mixture (to be separated) shows negative deviation
from ideality.
C. mixture (to be separated) shows positive deviation
from ideality.
D. multicomponent distillation is involved.
A
Pick out the correct statement.
A. In case of liquid-liquid extraction, no separation is
possible, if the selectivity of the solvent used is unity.
B. With increase in temperature, the selectivity of the
solvent used in solvent extraction decreases.
C. The selectivity of solvent used in solvent extraction is
unity at the plait point.
D. all (a), (b) and (c).
D
__________ columns are used for liquid dispersion in a
continuous gas phase.
A. Packed
B. Pulse
C. Bubble cap
D. Sieve plate
A
When the temperature and humidity of air is low, we usually use
__________ draft cooling tower.
A. natural
B. forced
C. induced
D. none of these
A
Overall efficiency of the distillation column is
A. the ratio of number of ideal plates to actual plates.
B. the ratio of number of actual plates to ideal plates.
C. same as the Murphree efficiency.
D. always more than the point efficiency.
A
On addition of solute in the solvent, the __________ of the
solution decreases.
A. boiling point
B. freezing point
C. vapour pressure
D. both (b) and (c)
D
Which is the controlling factor for a drum drier?
A. Diffusion
B. Heat transfer
C. Both (a) and (b)
D. Neither (a) nor (b)
B
The difference of wet bulb temperature and adiabatic saturation
temperature of unsaturated mix. of any system is
A. +ve
B. -ve
C. zero
D. none of these
A
Drying operation under vacuum is carried out to
A. dry those materials which have very high unbound
mositure content.
B. reduce drying temperature.
C. increase drying temperature.
D. dry materials having high bound moisture content
B
Air initially at 101. 3 kPa and 40°C and with a relative humidity
of 50%, is cooled at constant pressure to 30°C. The cooled air
has a
A. higher dew point.
B. higher absolute (specific) humidity.
C. higher relative humidity
D. higher wet bulb temperature.
C
Separation of two or more components of a liquid solution can
not be achieved by
A. fractional crystallisation
B. liquid extraction
C. absorption
D. Evaporation
C
Stefan’s law describes the mass transfer by
A. diffusion
B. bulk flow
C. both ‘a’ & ‘b’
D. neither ‘a’ nor ‘b’
C
At minimum reflux ratio for a given separation
A. number of plates is zero.
B. number of plates is infinity.
C. minimum number of the theoretical plates is required.
D. separation is most efficient.
B
Relative humidity is the ratio of the
A. partial pressure of the vapour to the vapour pressure
of the liquid at room temperature.
B. partial pressure of the vapour to the vapour pressure
of the liquid at gas temperature.
C. actual humidity to saturation humidity.
D. none of these
B
In batch distillation with constant reflux, overhead product
composition __________ with time.
A. increases
B. decreases
C. does not vary
D. may increase on decrease, depends on the system.
B
constant reflux=decrease
Psychrometry deals with the properties of gas-vapor mixture.
Humidity can be determined by the measurement of the
__________ of a fibre.
A. electrical resistance
B. thermal conductivity
C. strength
D. none of these.
A
Heat in BTU necessary to increase the temperature of 1 lb of
gas and its accompanying vapour by 1°F is called the
A. latent heat
B. humid heat
C. specific heat
D. sensible heat
C
To increase the absorption factor, (where, G = gas flow rate, S
= solvent flow rate)
A. increase both ‘G’ and ‘S’.
B. decrease both ‘G’ and ‘S’.
C. increase ‘S’ and decrease ‘G’.
D. increase ‘G’ and decrease ‘S’
C
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
A
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.
C
In a packed absorption tower, if the equilibrium and operating
lines are both straight lines, then the ratio, HETP/HTUOG
__________ the absorption factor.
A. increases with increase in
B. is one at unity value of
C. both (a) and (b)
D. neither (a) nor (b)
C
Which of the following plays an important role in problems of
simultaneous heat and mass transfer?
A. Lewis number
B. Schmidt number
C. Prandtl number
D. Sherwood number
A
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.
A
Absorption factor is defined as (where, S1 = slope of the
operating line S2 = slope of the equilibrium curve)
A. S2/S1
B. S1/S2
C. S1 - S2
D. S1 x S2
B
A plait point is the point on the solubility curve, where the tie
line reduces to a point. What is the number of plait point for a
ternary system containing 2 pairs of partially miscible liquids?
A. 0
B. 1
C. 2
D. 3
A
Which of the following remains constant during sensible
cooling process?
A. Specific humidity
B. Partial pressure of vapour
C. Both (a) and (b)
D. Neither (a) nor (b)
C
Physical absorption is
A. an irreversible phenomenon.
B. a reversible phenomenon.
C. accompanied by evolution of heat.
D. both (b) and (c)
D
Make up water is required in a cooling tower to replace the
water lost by
A. evaporation
B. drift
C. blowdown and leakage
D. all (a), (b) and (c)
D
Which of the following quantities need not be fixed before
starting the design of a co-current absorber ?
A. Heat gain or loss
B. Flow rate of entering liquid
C. Flow rate of gas
D. None of these
B
Mass transfer co-efficient of liquid is
A. affected more by temperature than that for gases.
B. affected much less by temperature than that for
gases.
C. not affected by the temperature.
D. none of these.
A
Absorption accompanied with chemical reaction is
exemplified by the absorption of
A. ammonia in water.
B. benzol present in coke oven gas by wash oil.
C. SO2 in alkaline solution.
D. all (a), (b) and (c).
C
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.
D
Which of the following liquid-vapor contacting devices
provides maximum contact surface area for a particular duty ?
A. Sieve plate column
B. Bubble cap column
C. Randomly packed column
D. Wetted wall column
D
The equipment frequently used for adiabatic humidification
cooling operation with recirculating liquid is
A. natural draft cooling tower
B. induced draft cooling tower
C. spray chamber
D. none of these
C
Chemisorption (chemical adsorption) is
A. same as “Van der Waals” adsorption.
B. characterised by adsorption of heat.
C. an irreversible phenomenon.
D. a reversible phenomenon.
C
Raoult’s law applies to the
A. all liquid solutions
B. non-ideal solution only.
C. non-volatile solute.
D. solvents
D
In distillation columns, the number of bubble caps per tray
primarily depends upon the
A. allowable liquid velocity.
B. allowable gas velocity.
C. allowable gas and liquid
D. feed composition.
C
In distillation, overhead product contains
A. only one component
B. two components
C. any number of components
D. only saturated liquid
C
When the liquid phase and vapour phase of a binary system
obeys Raoult’s and Dalton’s law respectively, the relative
volatility is the ratio of
A. vapour pressure of component A to that of
component B.
B. vapour pressure of component A to the total
pressure.
C. vapour pressure of component A to the partial
pressure of A.
D. partial pressure of component A to the total pressure.
A
With increase in pressure, the relative volatility for a binary
system
A. increases.
B. decreases.
C. remains same.
D. either (a) or (b), depends on the system.
B
Low viscosity absorbent is preferred for reasons of
A. rapid absorption rates and good heat transfer
characteristics.
B. improved flooding characteristics.
C. low pressure drop on pumping.
D. all (a), (b) and (c).
D
The rate of solid-liquid extraction is limited by the
A. phase change of the solute as it dissolves in the
solvent.
B. diffusion of the solute through the solvent in the pores
to the outside of the particle.
C. diffusion of the solute from the solution in contact with
the particle to the main bulk of the solution.
D. all ‘a’, ‘b’ & ‘c’.
D
Mass transfer co-efficient (K) and diffusivity (D) are related
according to film theory as
A. K ∝ D
B. K ∝SQRT D
C. K ∝ D1.5
D. K ∝ D2
A
The McCabe Δ L law states that the
A. molar heats of vaporisation of components are nearly
equal.
B. linear crystal growth rate depends on the degree of
supersaturation.
C. linear crystal growth rate does not depend on the crystal
size.
D. linear crystal growth rate depends on the crystal size.
C
Bollman extractor
A. is a static bed leaching equipment.
B. is used for extraction of oil from oilseed.
C. is a centrifugal extractor.
D. employs only counter-current extraction.
B
The relation, Sc = Pr = 1, is valid, when the mechanism of
__________ ansfer is same.
A. heat and mass
B. mass and momentum
C. heat and momentum
D. heat, momentum and mass
A
A coalescer in a mixer-settler liquid-liquid extraction coloumn
A. comprises of thin bed of substances of extended
surface having high porosity.
B. helps in increasing the bubble size entering the
settler.
C. helps in increasing the settling rate of the bubbles.
D. all ‘a’, ‘b’, & ‘c’.
D
For the same feed, feed quality and separation (in a distillation
column), with the increase of total pressure, the number of
ideal plates will
A. increase
B. decrease
C. remain same
D. data insufficient, can’t be predicted
A
The operation involved when the soluble material is largely on
the surface of an insoluble solid and is merely washed off by
the solvent is called
A. decoction
B. percolation
C. elutriation or elution
D. none of these
C
In the constant rate period of the rate of drying curve for batch
drying,
A. cracks develop on the surface of the solid.
B. rate of drying decreases abruptly.
C. surface evaporation of unbound moisture occurs.
D. none of these.
C
It takes 6 hours to dry a wet solid from 50% moisture content
to the critical moisture content of 15%. How much longer it will
take to dry the solid to 10% moisture content, under the same
drying conditions? (The equilibrium moisture content of the
solid is 5%).
A. 15 min
B. 51 min
C. 71 min
D. 94 min
C
Pick out the correct statement.
A. Ponchan-Savarit method is more accurate than
McCabe-Thiele method to determine the number of
theoretical stages required for the separation of non
ideal binary system by distillation.
B. A sharp decrease in pressure drop is an indication of
flooding in a distillation coloumn.
C. Solvent used in extractive distillation should be of
high volatility.
D. Flash distillation is suitable for separating
components which have very close boiling
temperature.
A
Agitator is provided in a crystalliser for
A. avoiding deposition on cooler surfaces.
B. formation of nuclei.
C. crystal growth.
D. all (a), (b) and (c).
D
_________ diffusion is used for separating the isotopes of
methane.
A. Thermal
B. Pressure
C. Concentration
D. Force
A
Ordinary diffusion process is also called __________
diffusion.
A. pressure
B. thermal
C. concentration
D. forced.
C
Pick out the wrong statement.
A. Different solids have different equilibrium moisture
curves.
B. Total condenser or reboiler is considered equivalent
to one theoretical plate in McCabe-Thiele method of
theoretical plate calculation for distillation column.
C. Heat removal load on cooler remains constant, even
with increase of the reflux ratio in a distillation
column.
D. Even a forced draft cooling tower can not cool water
below the wet bulb temperature.
C
The reason for preferring packed towers over plate towers in
distillation practice is that the packed tower operation gives
A. low pressure drop and high hold up.
B. high pressure drop and low hold up.
C. low pressure drop and low hold up.
D. high pressure drop and high hold up.
C
If the path of liquid across the plate is very long as in case of
large diameter tower, Murphree efficiency can be __________
percent.
A. 100
B. > 100
C. < 100
D. none of these
B
Pick out the wrong statement pertaining to the rotary dryer.
A. Flights (located in the inside shell of rotary dryer) lift
the material being dried and shower it down through
the current of hot air/gases. It extends from the wall
to a distance which is about 8-12% of the inside
diameter of shell.
B. Hold up of a rotary drier is defined as the fraction of
the dryer volume occupied by the solid at any instant.
The best performance for rotary drier is obtained,
when the hold up is in the range of 0.05 to 0.15.
C. Rotary dryer is suitable for drying sticky material.
D. Recommended peripherial speed of a rotary drier is
in the range of 10 to 30 metres/minute.
C
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. 25%
B. 50%
C. 70%
D. 90%
B
Raoult’s law is applicable to the
A. ideal solutions
B. real solutions
C. mixture of water and alcohol
D. non-ideal gases
A
Weeping in a distillation column
A. increases tray efficiency.
B. provides large interfacial surface for mass transfer.
C. results due to very high gas velocity.
D. results due to very low gas velocity.
D
In case of binary distillation, increasing the reflux ratio above
optimum does not result in the increase of
A. area between operating line and 45° diagonal x-y
diagram.
B. condenser and reboiler surfaces.
C. tower cross-section.
D. none of these.
A
Wetted wall tower experiment determines the
A. molal diffusivity.
B. volumetric co-efficient.
C. mass transfer co-efficient.
D. none of these.
C
In McCabe-Thiele method, at infinite reflux ratio
A. the overhead product is minimum.
B. both the operating lines coincide with diagonal.
C. both (a) and (b).
D. neither (a) nor (b).
A
Plate towers are preferred to packed towers, when large
temperature changes are involved, because of the reason that
the
A. packing may be crushed due to thermal
expansion/contraction of the components of the
equipments.
B. pressure drop in the equipment will be . very high.
C. viscosity variation of the fluids may cause
channeling/flooding.
D. none of these.
A
With decrease in the throughput (compared with the design
capacity) for a bubble cap distillation column, its efficiency
A. increases
B. decreases
C. remains same
D. may increase or decrease ; depends on individual
design
A
The equilibrium liquid composition compared to the vapor
composition in case of azeotropic mixture is
A. more
B. less
C. same
D. either more or less; depends on the system
C
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
A
Pick out the system with minimum boiling azeotrope at 1 atm.
A. benzene-toluene
B. ethyl alcohol-water
C. hydrochloric acid-water
D. all (a), (b) and (c)
B
Free flowing granular materials can be best dried in a
__________ drier.
A. rotary
B. cylinder
C. drun
D. freeze
A
In case of an ideal solution, the total vapor pressure varies
__________ with the composition expressed as mole fraction,
A. inversely
B. linearly
C. exponentially
D. none of these
B
Which of the following T-H diagram is valid for
dehumidification operation?
A. Operating line, Eq curve (/
B. eq curve, adiabatic saturation line
C. Operating line, Eq curve ))
A
Corresponding to Nusselt number in heat transfer, the
dimensionless group in mass transfer is the __________
number.
A. Sherwood
B. Schmidt
C. Peclet
D. Stanton
A
f the specific heats of a gas and a vapor are 0.2KJ/Kg.°K and
1.5 KJ/Kg.°K respectively, and the humidity is 0.01; the humid
heat in KJ/°Kg. is
A. 0.31
B. 0.107
C. 0.017
D. 0.215
D
Liquid diffusivity is of the order of __________ cm2 /second.
A. 0.01
B. 0.1
C. 10-5 to 10-6
D. 1
C
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.
D
At the same gas flow rate, the pressure drop in a packed
tower being irrigated with liquid __________ that in dry packed
tower.
A. is greater than
B. is lower than
C. is same as
D. cannot be predicted as data are insufficien
A
Molarity is defined as the number of gm moles of solute per
__________ of solvent.
A. litre
B. kg
C. gm
D. c.c
A
The value of Lewis number (Le = Sc/Pr) for air-water vapour
system is around
A. 1
B. 0.24
C. 3.97
D. 600
A
The partial pressure distribution of an ideal gas diffusing
through another stagnant ideal gas at steady state follows
a/an __________ law.
A. exponential
B. parabolic
C. linear
D. cubic
A
Pick out the correct statement.
A. Dialysis process is used for the production of fresh
water from brine.
B. Electrodylsis is used in the manufacture of NaOH.
C. Electrodylsis is used for the refin-ning/purification of
petrol.
D. both (b) and (c).
D
Very tall packed towers are divided into series of beds to
A. reduce the overall pressure drop
B. avoid channelling
C. reduce liquid hold-up
D. avoid flooding
B
Which of the following T-H diagram is valid for dehumidification
operation?
A. OP, EC (/
A
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.
A
Which of the following binary systems is an example of a
maximum boiling azeotrope ?
A. Water-hydrochloric acid.
B. Acetone-carbon disulphide.
C. Water-ethyl alcohol.
D. n-heptane-n-octane.
A
(NRe . NSc) is termed in mass transfer operation as the
__________ number.
A. Stanton
B. Sherwood
C. Peclet
D. none of these
C
The binary diffusivity in gases and liquids vary respectively as
A. T^3/2 and T
B. T and T^3/2
A
Pick out the correct statement.
A. The slope of the stripping line is always less than
unity.
B. For a given separation in a binary distillation column,
with increase in reflux ratio (above the minimum
reflux ratio), the fixed cost of the distillation column
first increases and then decreases.
C. In Ponchon-Savarit method of no. of theoretical plate
determination, the stripping and rectifying operating
lines are vertical at total reflux.
D. Kremsor-Brown-Souder’s equation is used to
calculate the efficiency of a plate tower.
C
Pick out the correct statement.
A. Bound moisture is removed during constant rate
drying period.
B. Free moisture is removed during falling rate drying
period.
C. The sum of free moisture and equilibrium moisture in
a solid is called the critical moisture.
D. The driving force for mass transfer in a wet solid is its
free moisture content.
D
Moisture contained by a substance in excess of the
equilibrium moisture is called the __________ moisture.
A. unbound
B. free
C. critical
D. bound
B
With increase in temperature, the solubility of gases in liquids,
at fixed pressure
A. increases
B. decreases
C. remains same
D. either (a) or (b), depends on the system
B
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
C
On moving the feed line (q-line) from saturated liquid feed
(vertical position) to saturated vapor feed (horizontal feed), if
the slope of both the operating lines are to be increased, then
it will result in
A. greater degree of separation with a fixed number of
trays
B. increased reboiler load
C. increased reflux ratio
D. None of these.
C
Pick out the wrong statement:
A. Reboiler is not used in open steam distillation.
B. The separation of solutes of different molecular sizes
in a liquid solution by use of a suitable membrane is
called dialysis.
C. Freeze drying is used for the drying of fish.
D. Fenske-Underwood equation is used for calculating
theoretical number of plates in a distillation column at
normal operating reflux condition.
D
Deairation (removal of O2) of water is done by
A. rectification
B. absorption
C. ion-exchange
D. Adsorption
C
__________ column is the most suitable for achieving the
best performance for mass transfer operations involving liquid
with dispersed solids.
A. Watted wall
B. Packed
C. Plate
D. Spray
C
best performance=plate
Make up water is supplied during cooling tower operation to
compensate for water losses due to
A. evaporation
B. blowdown
C. entrainment
D. all (a), (b)&(c)
D
Pick out the wrong statement.
A. The mole fraction of solute is directly proportional to
the molality of a ‘dilute’ solution.
B. For a non-reacting binary mixture of ideal gases, the
partial pressure distribution of both components is
nonlinear in the case of steady state unimolal
unidirectional diffusion.
C. Azeotropes obey Raoult’s law at all temperature.
D. The relative volatility of a binary mixture at the
azeotropic composition is 1.
C
A minimum boiling azeotrope is exemplified by
A. toluene-benzene
B. acetone-carbon disulphide
C. water-isobutyl alcohol
D. none of these
B
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).
A
Use of raschig rings in place of crushed stones as packing in
packed beds (other things being same)
A. increases pressure drop, increases surface area.
B. increases pressure drop, decreases surface area.
C. decreases pressure drop, increases surface area.
D. decreases pressure drop, decreases surface area.
C
Critical humidity of a solid salt means the humidity
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.
C
The assumption made in Elis method in distillation is that
enthalpy concentration lines of vapor and liquid are
A. parallel
B. straight
C. both parallel and straight
D. neither parallel nor straight
C
Pick out the wrong statement.
A. Critical moisture content is not a property of the
material itself.
B. A sharp increase in pressure drop gives an indication
of the flooding in a distillation column.
C. Separation of components is not possible in liquid
extraction, if selectivity is unity.
D. *Dehydration of ethyl alcohol is most economically
done by molecular distillation at very high vacuum.
B
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.
A
As complete saturation of an adsorbent is approached, the
differential heat of adsrop-tion approaches
A. that of normal condensation.
B. integral heat of adsorption.
C. zero.
D. none of these.
A
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.
A
The-relative volatility for separation of a non-ideal binary
mixture by distillation should be
A. 0
B. 1
C. > 1
D. < 1
C
In paper industry, paper is dried in a __________ dryer.
A. tunnel
B. heated cylinder
C. conveyor
D. festoon
B
Only small amount of evaporation of water produces large
cooling effects because of its
A. large latent heat
B. low viscosity
C. small latent heat
D. none of these
A
The most common packing used in industrial operations is
__________ rings.
A. raschig
B. lessing
C. cross-partition
D. single spiral
A
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
C
Leaching of sugar from sugar beets is done by
A. hot water
B. hexane
C. dilute H2SO4
D. lime water
A
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.
C
If f = moles of vapour present per mole of feed, then the slope
of feed line is (Mcabe-Thiele method)
A. 1-f/f
B. −f-1/f
C. −1/f
D. -f/1-f
C
At equilibrium the concentration of water in vapour phase
(C)in kg/m3 of air space and the amount of water (m)
adsorbed per kg of dry silica gel are related by, C = 0.0667m.
To maintain dry conditions in a room of air space 100m3
containing 2.2 kg of water vapour initially, 10 kg of dry silica
gel is kept in the room. The fraction of initial water remaining
in the air space after a long time (during which the temperature
is maintained constant) is
A. 0.0
B. 0.2
C. 0.4
D. 1.0
C
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.
D
The rate of mass transfer is not dependent upon the
A. degree of dispersion of one fluid in the other.
B. interfacial surface exposed between the phases.
C. both (a) & (b).
D. none of these.
D
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’
C
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. 0.60
B. 0.24
C. 1
D. 0.72
C
The reciprocal of stripping factor is termed as
A. selectivity index
B. relative volatility
C. absorption factor
D. Murphree efficiency
C
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.
C
The binary diffusivity in gases at atmospheric conditions is
about
A. 10-9 cm/sec
B. 10-1 cm2/sec
C. 10-3 sec/cm
D. 10-4 cm2/sec2
B
Percentage saturation is __________ the relative saturation.
A. always smaller than
B. always greater than
C. not related to
D. none of these
A
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.
B
What is the reflux ratio at total reflux ?
A. Zero
B. Infinity
C. Unity
D. Data insufficient
B
Under conditions of flooding in packed tower, the gas pressure
drop
A. decreases rapidly
B. increases rapidly
C. remains constant
D. is maximum
D
For achieving rapid drying rate in a spray dryer, the diameter
of the particles in the feed should be in the range of
__________ microns (1 mm = 1000 microns).
A. 1-5
B. 10-60
C. 200-300
D. 500
B
When acetone is added in a two layer mixture of methyl
isobutyl ketone and water at 30°C, the acetone distributes
between the two layers and the composition of the layer
follows two solubility curves. For this system,
A. as the acetone concentration increases, the solubility
curves approach each other.
B. both the phases become identical at a particular
common point on both the solubility curves called the
plait point.
C. the distribution curve which is a plot between x (acetone
concentration in one phase) and y (acetone
concentration in other phase) is analogous to x-y curve
used in distillation and absorption terminates on the x =
y diagonal at the concentration of the plait point.
D. all (a), (b) and (c).
D
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)
D
Prandtl number for water at 20°C is about
A. 7
B. 70
C. 0.7
D. 150.
A
The change in enthalpy per unit weight of adsorbed gas when
adsorbed on gas free or “outgassed” adsorbent to from a
definite concentration of adsorbate is called its
A. integral heat of adsorption.
B. heat of wetting.
C. differential heat of adsorption.
D. heat of normal condensation.
A
For absorbing a sparingly soluble gas in a liquid
A. gas side mass transfer co-efficient should be
increased.
B. liquid side mass transfer co-efficient should be
increased.
C. liquid side mass transfer co-efficient should be
decreased.
D. mass transfer co-efficient must be kept constant.
B
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
B
A good solvent used for absorption should not have very high
A. viscosity
B. vapor pressure
C. freezing point
D. all (a), (b) & (c)
D
In a counter-current liquid extractor
A. both liquids flow at fixed rate.
B. both liquids can have any desired flow rate.
C. only one of the liquids may be pumped at any desired
rate.
D. liquid’s flow rate depends upon the temperature and
pressure.
C
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
D
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.
A
Weight of 1 m3 of humid air as compared to 1 m3 of dry air,
under the same conditions, is
A. less
B. more
C. same
D. unpredictable
A
Pick out the wrong statement
A. Co-current absorbers are usually used, when the gas
to be dissolved in the liquid is a pure substance.
B. In case of gas absorption, HETP is equal to HTU,
when both the operating line & the equilibrium lines
are parallel.
C. Hatta number is important in case of gas absorption
with chemical reaction.
D. In actual practice, absorption is an en-dothermic
process, while stripping is an exothermic process.
D
Positive deviation from Raoult’s law means a mixture whose
total pressure is
A. greater than that computed for ideality.
B. less than that computed for ideality.
C. less than the sum of the vapour pressure of the
components.
D. none of these.
A
