Mass Transfer Flashcards
1
Q
Mass transfer rate between two fluid phases does not necessarily depend on the __________ of the two phases.
A
chemical properties
1
Q
Fenske equation determines the
A
minimum number of theoretical plates
2
Q
Total reflux in a distillation operation requires minimum
A
number of plates
2
Q
The term “cooling range” in a cooling tower refers to the difference in the temperature of
A
hot water entering the tower and the cooled water leaving the tower.
3
Q
The most suitable for extraction in a system having very low density difference ?
A
Centrifugal extractor
4
Q
The amount of steam required per unit quantity of distillate in case of steam distillation will be reduced by
A
both (a) and (b).
5
Q
Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the
A
relative volatility is reasonably constant.
6
Q
The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is
A
+ve
7
Q
When the temperature and humidity of air is low, we usually use __________ draft cooling tower.
A
natural
8
Q
Pick out the correct statement.
A
all (a), (b) and (c).
9
Q
__________ columns are used for liquid dispersion in a continuous gas phase.
A
Packed
10
Q
Overall efficiency of the distillation column is
A
the ratio of number of ideal plates to actual plates.
11
Q
the controlling factor for a drum drier
A
Heat transfer
11
Q
On addition of solute in the solvent, the __________ of the solution decreases.
A
both (b) and (c)
12
Q
Drying operation under vacuum is carried out to
A
reduce drying temperature.
13
Q
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 relative humidity
14
Q
Separation of two or more components of a liquid solution can not be achieved by
A
absorption
15
Q
Stefan’s law describes the mass transfer by
A
both ‘a’ & ‘b’
16
Q
At minimum reflux ratio for a given separation
A
number of plates is infinity.
17
Q
Relative humidity is the ratio of the
A
partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
18
Q
In batch distillation with constant reflux, overhead product composition __________ with time.
A
decreases
19
Q
Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the __________ of a fibre.
A
electrical resistance
20
Q
Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the
A
specific heat
21
Q
To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)
A
increase ‘S’ and decrease ‘G’.
22
In a packed absorption tower, if the equilibrium and operating lines are both straight lines, then the ratio, HETP/HTUOG __________ the absorption factor.
both (a) and (b)
22
Dew point of a gas-vapour mixture
decreases with decrease in pressure.
23
Which of the following plays an important role in problems of simultaneous heat and mass transfer ?
Lewis number
24
case of an absorber, the operating
line always lies above the equilibrium curve.
25
the reflux ratio in a distillation column is increased from the minimum, the
total cost first decreases and then increases.
26
Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)
S1/S2
27
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 ternery system containing twopairs of partially miscible liquids ?
0
28
the following remains constant during sensible cooling process ?
Both (a) and (b)
29
Physical absorption is
both (b) and (c)
30
Make up water is required in a cooling tower to replace the water lost by
all (a), (b) and (c)
31
the following quantities need not be fixed before starting the design of a co-current absorber ?
Flow rate of entering liquid
32
Mass transfer co-efficient of liquid is
affected more by temperature than that for gases.
33
Absorption accompanied with chemical reaction is exemplified by the absorption of
SO2 in alkaline solution.
34
he following unit operations makes use of Thiele-Geddes equation
Multicomponent distillation.
35
the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty
Wetted wall column
36
The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is
spray chamber
37
Chemisorption (chemical adsorption) is
an irreversible phenomenon.
38
The rate of solid-liquid extraction is limited by the
all 'a', 'b' & 'c'
39
Raoult's law applies to the
solvents.
40
In distillation columns, the number of bubble caps per tray primarily depends upon the
allowable gas and liquid velocities.
41
distillation, overhead product contains
any number of components
42
Low viscosity absorbent is preferred for reasons of
all (a), (b) and (c).
43
The McCabe Δ L law states that the
linear crystal growth rate does not depend on the crystal size.
44
increase in pressure, the relative volatility for a binary system
decreases.
45
Bollman extractor
is used for extraction of oil from oilseed.
45
The relation, Sc = Pr = 1, is valid, when the mechanism of __________ ansfer is same.
heat and mass
46
A coalescer in a mixer-settler liquid-liquid extraction coloumn
all 'a', 'b', & 'c'.
47
For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will
Incease
48
Pick out the correct statement.
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.
49
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
vapour pressure of component A to that of component B.
50
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
elutriation or elution
51
In the constant rate period of the rate of drying curve for batch drying,
surface evaporation of unbound moisture occurs.
52
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%).
71 min
53
Agitator is provided in a crystalliser for
all (a), (b) and (c).
54
__________ diffusion is used for separating the isotopes of methane.
Thermal
55
Ordinary diffusion process is also called __________ diffusion.
concentration
55
Pick out the wrong statement.
Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
56
Pick out the wrong statement pertaining to the rotary dryer.
Rotary dryer is suitable for drying sticky material.
57
The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives
low pressure drop and low hold up.
58
If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent.
> 100
59
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
50%
60
Raoult's law is applicable to the
ideal solutions
60
Weeping in a distillation column
results due to very low gas velocity.
60
Wetted wall tower experiment determines the
mass transfer co-efficient.
61
In McCabe-Thiele method, at infinite reflux ratio
the overhead product is minimum.
61
With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency
increases
62
Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the
packing may be crushed due to thermal expansion/contraction of the components of the equipments.
62
The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is
same
63
Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.
wetted wall
64
Pick out the system with minimum boiling azeotrope at 1 atm.
ethyl alcohol-water
65
Free flowing granular materials can be best dried in a __________ drier.
rotary
66
In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction,
linearly
67
Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number.
Sherwood
68
The solvent used in liquid extraction should not have high latent heat of vaporization, because
its recovery cost by distillation may be prohibitatively high.
69
Molarity is defined as the number of gm moles of solute per __________ of solvent.
litre
69
At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid __________ that in dry packed tower.
is greater than
70
The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.
exponential
71
the following binary systems is an example of a maximum boiling azeotrope
Water-hydrochloric acid.
71
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)
less number of trays are required.
72
(NRe . NSc) is termed in mass transfer operation as the __________ number.
Peclet
73
Pick out the correct statement.
In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.
74
Pick out the correct statement.
The driving force for mass transfer in a wet solid is its free moisture content.
74
Pick out the correct statement.
Electrodylsis is used in the manufacture of NaOH.
75
Very tall packed towers are divided into series of beds to
avoid channeling
76
Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture.
free
77
With increase in temperature, the solubility of gases in liquids, at fixed pressure
decreases
78
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
increased reflux ratio
78
__________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids.
Plate
78
Deliration (removal of O2) of water is done by
ion-exchange
79
Make up water is supplied during cooling tower operation to compensate for water losses due to
all (a), (b)&(c)
80
Pick out the wrong statement.
Azeotropes obey Raoult's law at all temperature
81
A minimum boiling azeotrope is exemplified by
acetone-carbon disulphide
82
the following solutions will follow Raoult's law most closely
A solution of benzene, toluene and oxylene.
83
Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)
decreases pressure drop, increases surface area.
84
Critical humidity of a solid salt means the humidity
both (a) and (b).
85
The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are
both parallel and straight
86
Pick out the wrong statement:
Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.
86
Only small amount of evaporation of water produces large cooling effects because of its
large latent heat
87
The-relative volatility for separation of a non-ideal binary mixture by distillation should be
> 1
87
In paper industry, paper is dried in a __________ dryer.
heated cylinder
87
When the feed to a distillation column is a saturated liquid, slope of the feed line is
infinity
87
As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches
that of normal condensation.
88
Pick out the wrong statement.
Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.
88
The most common packing used in industrial operations is __________ rings.
raschig
88
Leaching of sugar from sugar beets is done by
hot water
89
Absorption with chemical reaction' is involved in the removal of
carbon dioxide from gaseous stream using alkaline solution.
90
Absorption factor method is used to calculate the number of ideal stages, when
both operating and equilibrium lines are parallel.
90
Flights in a rotary dryer are provided to
lift and shower the solids thus exposing it thoroughly to the drying action of the gas.
90
The rate of mass transfer is not dependent upon the
none of these.
90
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
on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.
90
Dry bulb temperature of unsaturated air is more than its __________ temperature.
both 'a' & 'b'
90
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
1
90
In case of a desorber (stripper), the
operating line always lies below the equilibrium curve.
91
Ponchan-Savarit method analyses the fractional equipment based on
both enthalpy and material balances.
92
The reciprocal of stripping factor is termed as
absorption factor
92
Percentage saturation is __________ the relative saturation.
always smaller than
92
What is the reflux ratio at total reflux ?
Infinity
92
Under conditions of flooding in packed tower, the gas pressure drop
is maximum
93
absorbing a sparingly soluble gas in a liquid
liquid side mass transfer co-efficient should be increased.
93
Channelling in a packed tower results from the
both (b) and (c)
93
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
integral heat of adsorption.
93
The minimum number of theoretical plates is required for achieving a given separation in distillation column with
total reflux
94
A good solvent used for absorption should not have very high
all (a), (b) & (c)
94
In a counter-current liquid extractor
only one of the liquids may be pumped at any desired rate.
95
the following is an undesirable property for an absorbing solvent
None of these
95
The wetted wall tower is used to determine
individual mass transfer co-efficient (M.T.C.) in gaseous system.
95
With increase in gas rate, the number of transfer units, NtoG, for a fixed degree of absorption by a fixed amount of solvent
increases
95
Positive deviation from Raoult's law means a mixture whose total pressure is
greater than that computed for ideality.
95
Prandtl number for water at 20°C is about
7
95
The caking of crystals can be prevented by
both (a) and (c)
96
Boiling point diagram is
affected by pressure.
97
A slurry is to be dried to produce flaky solid. Which dryer would you recommend ?
Spray dryer
98
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,
all (a), (b) and (c).
98
Freundlich equation applies to the adsorption of solute from
dilute solutions, over a small concentration range.
98
Steam distillation is used to
avoid thermal decomposition of a component.
98
For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.
marginal decrease in the number of
98
The apex of an equilateral-triangular coordinate (in ternary liquid system) represents a/an
pure component
99
The humid volume may be increased by increasing the
both (a) and (b).
99
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.
steam
99
Azeotropic distillation is employed to separate
constant boiling mixture.
99
Large scale drying of wheat is done in a __________ dryer.
spouted bed
99
At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes
∞
100
Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent ?
Heating and dehumidification at almost constant wet bulb temperature.
100
Dimension of mass diffusivity is the same as that of
kinematic viscosity
100
Pick out the wrong statement
In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.
100
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 )
T2
100
an undesirable property in a tower packing
Large weight of liquid retained.
100
Humidity chart is useful for the solution of problems concerning condensation, vaporization and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.
molal
101
Water entrained by circulating air in cooling towers is termed as
drift
101
Steam distillation is used to separate
high boiling substances from nonvolatile impurities.
101
In an absorption coloumn, the flooding velocity for random packing is __________ that for stacked/regular packing.
smaller than
102
Use of natural draft cooling tower is practiced, when the air has low
both 'a' & 'b'
102
Blowdown in a cooling tower
means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.
102
The fixed cost of a distillation column at minimum reflux ratio is
infinite
102
Pressure drop through plate tower as compared to that through packed tower, for the same duty will be
more
103
With increase in temperature, the leaching rate increases because of the
both (a) and (b).
103
In case of constant underflow extraction operation, the __________ at all solute concentration.
both(a) & (b)
103
Leaching of uranium ore and gold ore is done in
Pachuka tanks
103
Dorr thickener is an equipment used for
sedimentation
103
Antibiotics are best handled in a
Podbielniak extractor.
103
increase in temperature, the rate of leaching increases, because the
diffusivity of solute increases.
103
Pick out the wrong statement.
Mechanical agitation is required, if the system has low interfacial tension.
104
To get high tray efficiency
interfacial surface between liquid and gas phase should be large.
104
__________ extractor uses centrifugal force for separating the two phases.
Podbielniak
104
In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in
all 'a', 'b' & 'c'.
104
A natural draft cooling tower is filled with wooden grids, which covers about __________ percent of the tower height.
10-15
104
Desulphurization of petrol is done in a
rotating disc extractor
104
Pick out the system with maximum boiling azeotrope at 1 atm.
acetone chloroform
104
During constant rate period, the rate of drying decreases with the
both (a) and (b)
105
The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if
NSc = NPr = NLe
105
In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of
-1.5
105
Acetic acid will be most economically separated from a dilute solution of acetic acid in water by
solvent extraction
105
The mass transfer co-efficient for a solid sphere of radius 'a' dissolving in a large volume of quiescent liquid, in which D is the diffusivity of solute, is
dependent on the Reynolds number
106
Design calculation for multiple component distillation is done by
tray to tray calculations.
106
Reboiler is considered as one theoretical plate, because
of the assumption that vapor and liquid leaving the reboiler are in equilibrium.
106
the following is not a batch drier?
Fluidised bed drier
106
Mass transfer co-efficient 'K' according to penetration theory varies with mass diffusivity as
D0.5
106
The relative saturation of a partially saturated mixture of vapour and gas can be increased by __________ of the mixture.
both (b) and (c)
107
The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the
differential heat of adsorption.
107
At 750°K and 1 atm, the approximate value of Schmidt number for air is
0.1
107
Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant
all (a), (b) & (c)
107
Calculation of mass transfer co-efficient is mostly/normally done using __________ theory.
film
108
As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages
decrease
108
Pick out the wrong statement. Generally for physical adsorption, a gas of
none of these.
109
Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be
humidified
109
In triangular co-ordinates, the ternary composition point falls __________ of the triangle.
inside
110
For absorbing a sparingly soluble gas in a liquid, the
liquid side coefficient should be increased.
110
In a gas-liquid absorption coloumn, for obtaining the maximum absorption efficiency
both gas as well as liquid streams should be distributed uniformly.
110
Most important factor to be considered in the selection of packings for absorbers is the __________ of packing.
porosity
110
The boiling points of pure components of a binary system __________ with increase in total pressure of the system.
increases
110
provides maximum contact surface for a liquid-vapour system
Packed tower
110
Danckwerts developed the __________ theory.
surface renewal
110
Molality is defined as the number of gm moles of solute per __________ of solvent.
Kg
110
Chemisorption compared to physical absorption has
increased utilization of stagnant zones of the liquid phase.
110
In the layout plan for a vacuum distillation unit, operating at 60 mm Hg, supported by a barometric condenser, the appropriate place for the location of vacuum drum for collecting the distillate will be
at ground level.
110
During constant rate drying period, vaporization rate per unit drying surface area
does not change with time,
110
Molecular distillation is
both (b) and (c)
111
Rate of adsorption increases as the
temperature decreases.
111
used for the concentration of rubber latex
Agitated film evaporator
111
For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is
known
111
stripping section of continuous distillation column, the
liquid is enriched with high boiler.
111
Fractional solvent extraction
employs two solvents
111
Pick out the wrong statement.
Mass transfer co-efficient does not account for gas-liquid diffusion.
111
Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)
(4De/πt)1/2
111
In rectifying section of a continuous distillation column, the
vapour is enriched with high boilers.
111
Steam distillation is not recommended to be used, if the
azeotropic mixture is to be separated and the final product is miscible with water.
111
Reverse osmosis is also called
ultrafiltration.
112
Rayleigh equation applies to __________ distillation.
differential
112
__________ is the separation technique used for desalination of sea water.
Reverse osmosis
112
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
increases
112
Flooding in a distillation column is detected by a sharp
increase in pressure drop.
112
In case of unsaturated air
both (a) and (b)
112
At constant pressure, with increase of temperature, the dew point will
increase
112
Absorption accompanied by heat evolution results in
decrease in equilibrium solubility.
112
Flash distillation is suitable for the separation of components
having very wide boiling points.
113
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
1.24
113
Raschig ring made of procelain cannot be used for treating concentrated
alkalis
113
__________ is concerned with the adsorption equilibria.
Freundlich equation
113
Minimum reflux ratio in a distillation column results in
maximum condenser size.
113
In extraction, as the temperature increases, the area of hetrogeneity (area covered by binodal curve)
decreases
113
H2S present in naphtha reformed gas is removed by absorbing with
ethanolamine
113
In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation.
lower than
113
For a single component absorber, the operating line is straight only when plotted in term of __________ units.
mole ratio
114
For a binary mixture with low relative volatility,
an azeotrope may be formed during distillation.
114
Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the
high pressure drop of the gas.
114
Leaching rate is independent of the
none of these
114
For a distillation column operating at minimum reflux, the
number of plates required will be maximum.
114
Plate efficiency
is a function of the mass transfer between liquid and vapour.
115
In Mcabe-Thiele method, at infinite reflux ratio
both the operating lines coincide with the diagram.
116
The cooling effect in a cooling tower can not be increased by
none of these.
117
Use of packed towers for distillation is generally limited to the
small sizes
118
Pick out the wrong statement.
Molecular diffusion in solid is much faster than that in liquids.
118
decreases during evaporative cooling process with recirculated water supply
None of these
118
The minimum liquid rate to be used in an absorber corresponds to an operating line
tangential to the equilibrium curve
118
Perforated plate towers are unique for solvent extraction because, they provide
repeated coalescence & redispersion of the drop phase.
118
Laboratory determination of the diffusivity of vapor is done by __________ method.
Winkel mann's
118
n case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of __________ is zero.
interface
119
Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations.
Reynolds number in mass transfer is analogous to Grashoff number in heat transfer
119
The individual mass transfer co-efficients (moles/m2 . s) for absorption of a solute from a gas mixture into a liquid solvent are, KL = 4.5 and KG = 1.5. The slope of the equilibrium line is 3. Which of the following resistance (s) is (are) controlling ?
gas side
120
Pore size of the molecular seive 5A is __________ mm.
0.5
120
Swenson-Walker crystalliser is a __________ unit
continuous
120
Absorption (liquid-gas system) with evolution of heat as compared to isothermal absorption results in
all (a), (b) and (c).
121
increase in temperature, the mutual solubility of two liquids
increases
121
Pick out the wrong statement
The capacity of a distillation column is maximum at total reflux.
121
Relative volatility varies with the concentration of component for an ideal solution. The relative volatity of a binary mixture may be defined as the ratio of vapor pressure of component 'A' to that of component 'B', when
Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.
121
High pressure at the bottom of a distillation tower handling heat sensitive materials results in
thermal decomposition of bottoms.
121
Lewis number (Le) is
Sc / Pr
122
Alcohol is dehydrated using __________ distillation.
azeotropic
122
Separation of two volatile liquids by distillation makes use of their
relative volatility
122
Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.
tray
122
Pick out the wrong statement:
The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.
122
following increases during evaporative cooling process with recirculated water supply
Both (b) and (c)
122
the difference between heat of adsorption and heat of normal condensation is
equal to the heat of wetting.
122
parameters remains constant during chemical dehumidification
Dry bulb temperature
122
Large scale usage of flash distillation is practiced in
petroleum refinning
123
Drying of a solid involves __________ transfer.
both heat and mass
123
Mechanism of moisture removal in case of freeze drying of food stuff is by
sublimation
124
The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture.
temperature
124
not concerned directly with mass transfer
Froude number
124
Removal of __________ exemplifies an adsorption unit operation.
water from petrol
125
With increase in the mass velocity of the gas, the rate of drying during the constant rate period __________ , if the conduction and radiation through the solid are negligible.
increases
125
For gas absorption, low viscosity solvents are preferred, because of their
all (a), (b) and (c).
126
To remove all the moisture from a wet solid it requires exposure to __________ air.
perfectly dry
127
Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the __________ temperature.
wet-bulb
128
The slope of 9-line is determined by the
thermal condition of the feed
129
In steam distillation, the
product must be immiscible with water.
130
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