MASA PASA Flashcards
1
Q
Mass transfer rate between two fluid phases does not necessarily depend on the __________ of the two phases.
A
A. chemical properties
2
Q
In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is
A
A. 0.5
3
Q
Fenske equation determines the
A
C. minimum number of theoretical plates.
4
Q
The term “cooling range” in a cooling tower refers to the difference in the temperature of
A
C. hot water entering the tower and the cooled water leaving the tower.
5
Q
Which of the following is the most suitable for extraction in a system having very low density difference?
A
B. Centrifugal extractor
6
Q
Total reflux in a distillation operation requires minimum
A
B. number of plates
7
Q
The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is
A
A. (+)ve
8
Q
Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the
A
A. relative volatility is reasonably constant.
9
Q
When the temperature and humidity of air is low, we usually use __________ draft cooling tower.
A
A. natural
10
Q
Pick out the correct statement.
A
D. all (a), (b) and (c). (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.)
11
Q
__________ columns are used for liquid dispersion in a continuous gas phase.
A
A. Packed
12
Q
Overall efficiency of the distillation column is
A
A. the ratio of number of ideal plates to actual plates.
13
Q
Which is the controlling factor for a drum drier?
A
B. Heat transfer
14
Q
Drying operation under vacuum is carried out to
A
B. reduce drying temperature.
15
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
C. higher relative humidity
16
Q
Separation of two or more components of a liquid solution can not be achieved by
A
C. absorption
17
Q
At minimum reflux ratio for a given separation
A
B. number of plates is infinity.
18
Q
Relative humidity is the ratio of the
A
B. partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
19
Q
In batch distillation with constant reflux, overhead product composition __________ with time.
A
B. decreases
20
Q
Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the __________ of a fibre.
A
A. electrical resistance
21
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
C. specific heat
22
Q
To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)
A
C. increase ‘S’ and decrease ‘G’.
23
Q
The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________
A
A. 1
24
Q
Dew point of a gas-vapour mixture
A
C. decreases with decrease in pressure.
25
Which of the following plays an important role in problems of simultaneous heat and mass transfer?
A. Lewis number
26
In case of an absorber, the operating
A. line always lies above the equilibrium curve.
27
As the reflux ratio in a distillation coloumn is increased from the minimum, the
C. total cost first decreases and then increases.
28
Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)
B. S1/S2
29
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?
A. 0
30
Make up water is required in a cooling tower to replace the water lost by
D. all (a), (b) and (c) (A. evaporation) (B. drift) (C. blowdown and leakage)
31
Which of the following quantities need not be fixed before starting the design of a co-current absorber?
B. Flow rate of entering liquid
32
Mass transfer co-efficient of liquid is
A. affected more by temperature than that for gases.
33
Absorption accompanied with chemical reaction is exemplified by the absorption of
C. SO2 in alkaline solution.
34
Which of the following unit operations makes use of Thiele-Geddes equation?
D. Multicomponent distillation.
35
Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty?
D. Wetted wall column
36
The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is
C. spray chamber
37
Chemisorption (chemical adsorption) is
C. an irreversible phenomenon.
38
The rate of solid-liquid extraction is limited by the
D. all 'a', 'b' & 'c'. (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. )
39
Raoult's law applies to the
D. solvents.
40
In distillation columns, the number of bubble caps per tray primarily depends upon the
C. allowable gas and liquid velocities.
41
In distillation, overhead product contains
C. any number of components
42
With increase in pressure, the relative volatility for a binary system
B. decreases.
43
Low viscosity absorbent is preferred for reasons of
D. all (a), (b) and (c). (A. rapid absorption rates and good heat transfer characteristics.) (B. improved flooding characteristics.) (C. low pressure drop on pumping.)
44
Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as
A. K ∝ D
45
The McCabe Δ L law states that the
C. linear crystal growth rate does not depend on the crystal size.
46
Bollman extractor
B. is used for extraction of oil from oilseed.
47
The relation, Sc = Pr = 1, is valid, when the mechanism of __________ ansfer is same.
A. heat and mass
48
A coalescer in a mixer-settler liquid-liquid extraction coloumn
D. all 'a', 'b', & 'c'. (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.)
49
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
50
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.
51
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.
52
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
C. elutriation or elution
53
In the constant rate period of the rate of drying curve for batch drying,
C. surface evaporation of unbound moisture occurs.
54
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%).
C. 71 min
55
Agitator is provided in a crystalliser for
D. Dall (a), (b) and (c). (A. avoiding deposition on cooler surfaces.) (B. formation of nuclei.) (C.crystal growth.)
56
__________ diffusion is used for separating the isotopes of methane.
A. Thermal
57
Ordinary diffusion process is also called __________ diffusion.
C. concentration
58
Pick out the wrong statement.
C. Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
59
Pick out the wrong statement pertaining to the rotary dryer.
C. Rotary dryer is suitable for drying sticky material.
60
The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives
C. low pressure drop and low hold up.
61
If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent.
B. > 100
62
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
B. 0.5
63
Raoult's law is applicable to the
A. ideal solutions
64
Weeping in a distillation column
D. results due to very low gas velocity.
65
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.
66
Wetted wall tower experiment determines the
C. mass transfer co-efficient.
67
In McCabe-Thiele method, at infinite reflux ratio
A. the overhead product is minimum.
68
With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency
A. increases
69
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.
70
The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is
C. same
71
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
72
Pick out the system with minimum boiling azeotrope at 1 atm.
B. ethyl alcohol-water
73
Free flowing granular materials can be best dried in a __________ drier.
A. rotary
74
In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction,
B. linearly
75
Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number.
A. Sherwood
76
If 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
D. 0.215
77
Liquid diffusivity is of the order of __________ cm2 /second.
C. 10-5 to 10-6
78
The solvent used in liquid extraction should not have high latent heat of vaporisation, because
C. its recovery cost by distillation may be prohibitatively high.
79
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
80
Molarity is defined as the number of gm moles of solute per __________ of solvent.
A. liter
81
The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around
A. 1
82
Which of the following T-H diagram is valid for dehumidification operation?
A.
83
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.
84
The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.
A. exponential
85
Which of the following binary systems is an example of a maximum boiling azeotrope?
A. Water-hydrochloric acid.
86
(NRe . NSc) is termed in mass transfer operation as the __________ number.
C. Peclet
87
The binary diffusivity in gases and liquids vary respectively as
A. T^3/2 and T
88
Pick out the correct statement.
C. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.
89
Pick out the correct statement.
B. Electrodylsis is used in the manufacture of NaOH.
90
Pick out the correct statement.
D. The driving force for mass transfer in a wet solid is its free moisture content.
91
Very tall packed towers are divided into series of beds to
B. avoid channelling
92
Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture.
B. free
93
With increase in temperature, the solubility of gases in liquids, at fixed pressure
B. decreases
94
In most of the vacuum crystalliser, vacuum is generally produced by means of a
C. steam jet ejector with a barometric condenser
95
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
C. increased reflux ratio
96
__________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids.
C. Plate
97
Deairation (removal of O2) of water is done by
C. ion-exchange
98
Make up water is supplied during cooling tower operation to compensate for water losses due to
D. all (a), (b)&(c) (A.evaporation ) (B. blowdown) (C. entrainment)
99
Pick out the wrong statement.
C. Azeotropes obey Raoult's law at all temperature.
100
A minimum boiling azeotrope is exemplified by
B. acetone-carbon disulphide
101
Which of the following solutions will follow Raoult's law most closely?
A. A solution of benzene, toluene and oxylene.
102
Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)
C. decreases pressure drop, increases surface area.
103
The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are
C. both parallel and straight
104
As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches
A. that of normal condensation.
105
Absorption with chemical reaction' is involved in the removal of
A. carbon dioxide from gaseous stream using alkaline solution.
106
The-relative volatility for separation of a non-ideal binary mixture by distillation should be
C. > 1
107
Pick out the wrong statement:
D. Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.
108
In paper industry, paper is dried in a __________ dryer.
B. heated cylinder
109
Pick out the wrong statement.
D. Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.
110
Only small amount of evaporation of water produces large cooling effects because of its
A. large latent heat
111
The most common packing used in industrial operations is __________ rings.
A. raschig
112
When the feed to a distillation column is a saturated liquid, slope of the feed line is
C. infinity
113
Leaching of sugar from sugar beets is done by
A. hot water
114
Absorption factor method is used to calculate the number of ideal stages, when
C. both operating and equilibrium lines are parallel.
115
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.
116
If f = moles of vapour present per mole of feed, then the slope of feed line is (Mcabe-Thiele method)
C. -1/f
117
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
D. on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.
118
The rate of mass transfer is not dependent upon the
D. none of these. (A. degree of dispersion of one fluid in the other.) (B. interfacial surface exposed between the phases.)
119
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
C. 0.4
120
Dry bulb temperature of unsaturated air is more than its __________ temperature.
C. both 'a' & 'b'
121
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
C. 1
122
The reciprocal of stripping factor is termed as
C. absorption factor
123
Ponchan-Savarit method analyses the fractional equipment based on
C. both enthalpy and material balances.
124
The binary diffusivity in gases at atmospheric conditions is about
B. 10^-1 cm2/sec
125
Percentage saturation is __________ the relative saturation.
A. always smaller than
126
In case of a desorber (stripper), the
B. operating line always lies below the equilibrium curve.
127
What is the reflux ratio at total reflux?
B. Infinity
128
Under conditions of flooding in packed tower, the gas pressure drop
D. is maximum
129
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).
B. 10-60
130
For absorbing a sparingly soluble gas in a liquid
B. liquid side mass transfer co-efficient should be increased.
131
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.
132
The minimum number of theoretical plates is required for achieving a given separation in distillation column with
B. total reflux
133
A good solvent used for absorption should not have very high
D. all (a), (b) & (c) (A. viscosity) (B. vapor pressure) (C. freezing point)
134
In a counter-current liquid extractor
C. only one of the liquids may be pumped at any desired rate.
135
Which of the following is an undesirable property for an absorbing solvent ?
D. None of these (A. Low vapour pressure) (B. Low velocity) (C. Low freezing point)
136
The wetted wall tower is used to determine
A. individual mass transfer co-efficient (M.T.C.) in gaseous system.
137
Weight of 1 m3 of humid air as compared to 1 m3 of dry air, under the same conditions, is
A. less
138
Positive deviation from Raoult's law means a mixture whose total pressure is
A. greater than that computed for ideality.
139
With increase in gas rate, the number of transfer units, NtoG, for a fixed degree of absorption by a fixed amount of solvent
A. increases
140
Schmidt number is given by
A. μ/ρDAB
141
Prandtl number for water at 20°C is about
A. 7
142
Boiling point diagram is
B. affected by pressure.
143
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,
D. all (a), (b) and (c) (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.)
144
Steam distillation is used to
B. avoid thermal decomposition of a component.
145
Freundlich equation applies to the adsorption of solute from
A. dilute solutions, over a small concentration range.
146
For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.
B. marginal decrease in the number of
147
The apex of an equilateral-triangular coordinate (in ternary liquid system) represents a/an
A. pure component
148
The diffusivity (D) in a binary gas mixture is related to the pressure (P) as
C. D ∝ 1/P
149
A slurry is to be dried to produce flaky solid. Which dryer would you recommend?
A. Spray dryer
150
Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent?
B. Heating and dehumidification at almost constant wet bulb temperature.
151
In gas-liquid contact operation, the number of ideal stages, (np picture) . This is true when the stripping factor 'S' is
A. S > 1
152
The cooling effect in a cooling tower can not be increased by
D. none of these. (A. increasing the air velocity over the wet surfaces.) (B. reducing the humidity of entering air.) (C. lowering the barometric pressure.)
153
The value of NA/(NA + NB) for steady state molecular diffusion of gas 'A' through non-diffusing gas 'B' is
A. 1
154
Pick out the wrong statement
D. In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.
155
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.
B. steam
156
Large scale drying of wheat is done in a __________ dryer.
B. spouted bed
157
Azeotropic distillation is employed to separate
A. constant boiling mixture.
158
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)
C. T^2
159
At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes
C. ∞
160
Pressure drop through plate tower as compared to that through packed tower, for the same duty will be
B. more
161
Dimension of mass diffusivity is the same as that of
A. kinematic viscosity
162
Dorr thickener is an equipment used for
B. sedimentation
163
Steam distillation is used to separate
B. high boiling substances from nonvolatile impurities.
164
In distillation where q is defined as the moles of liquid flow in the stripping section per mole of feed introduced, for saturated liquid feed
C. q = 1
165
Which of the following is an undesirable property in a tower packing?
D. Large weight of liquid retained.
166
Water entrained by circulating air in cooling towers is termed as
A. drift
167
A 25 cm x 25 cm x 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m x 1m x 1cm flat sheet of the same material is to be dried from one side only.Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is
A. 1000
168
With increase in temperature, the rate of leaching increases, because the
A. diffusivity of solute increases.
169
Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.
molal
A. molal
170
The Kundsen diffusivity is proportional to (where, T = absolute temperature)
A. sqrt(T)
171
In an absorption coloumn, the flooding velocity for random packing is __________ that for stacked/regular packing.
B. smaller than
172
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.)
C. Kc = Kp . RT = Km . RT/p
173
Leaching of uranium ore and gold ore is done in
B. Pachuka tanks
174
Blowdown in a cooling tower
A. means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.
175
Antibiotics are best handled in a
A. Podbielniak extractor.
176
The fixed cost of a distillation column at minimum reflux ratio is
B. infinite
177
__________ extractor uses centrifugal force for separating the two phases.
C. Podbielniak
178
In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of
C. -1.5
179
Pick out the wrong statement.
A. Mechanical agitation is required, if the system has low interfacial tension.
180
Acetic acid will be most economically separated from a dilute solution of acetic acid in water by
A. solvent extraction
181
Design calculation for multiple component distillation is done by
D. tray to tray calculations.
182
To get high tray efficiency
A. interfacial surface between liquid and gas phase should be large.
183
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
D. dependent on the Reynolds number
184
Pick out the wrong statement. Generally for physical adsorption, a gas of
D. none of these. (A. higher molecular weight is adsorbed in preference to a gas of low molecular weight.) (B. high critical temperature is adsorbed in preference to a gas of low critical temperature.) (C. low volatility is adsorbed in preference to a gas of high volatility.)
185
In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in
D. all 'a', 'b' & 'c'. (A. reducing the axial mixing.) (B. increasing the rate of extraction.) (C. maintaining the concentration difference between the two phases.)
186
In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as
B. 1/KG = 1/KG + m/KL
187
Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when
D. one of the liquid components has very high affinity towards the solvent.
188
Inside the distillation column, the
A. driving force for the vapour flow is the pressure drop.
189
Occurrence of 'case hardening' during drying of a high moisture solid cake __________ the drying rate.
B. decreases
190
Which of the following is not a continuous drier?
D. Tray drier
191
Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is
A. insoluble in the liquid
192
__________ is the temperature at which a gas-vapor mixture becomes saturated, when cooled at constant total pressure out of contact with a liquid.
A. Dew point
193
Rate of leaching increases with increasing
A. temperature
194
An azeotropic mixture is a __________ mixture.
C. constant boiling point
195
Pick out the wrong statement.
C. For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10-2m/s. Then the average mass transfer co-efficient for the plate is 2 x 10-2m/s.
196
Molecular seives are regenerated by heating to __________ °C.
B. 200-330
197
In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as
. Ri = Re/1+Re
198
In a counter-current extractor, as the axial mixing increases, the extraction efficiency
B. decreases
199
Heat sensitive materials like certain pharmaceuticals and food stuffs can be dried in a/an __________ dryer.
C. freeze
200
In extractive distillation, solvent is
A. added to alter the relative volatility of the mixture.
201
Radioactive nuclear waste is treated in
C. pulsed column extractor
202
Large scale drying of sugar is done in a __________ dryer.
C. rotary
203
__________ temperature is the steady state temperature attained by a small amount of liquid evaporating into a large quantity of unsaturated gas-vapor mixture.
B. Wet bulb
204
The drying time between fixed moisture contents within the 'constant rate period' is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid)
B. T
205
__________ equation applies to diffusivities in liquids.
A. Gilliland
206
A packed tower compared to a plate tower for a particular mass transfer operation
A. incurs smaller pressure drop.
207
Which of the following is the most commonly used leaching solvent in vegetable oil industry?
B. Hexane
208
In an absorber, HETP does not vary with the
D. none of these (A. flow rate of liquid) (B. flow rate of gas) (C. type and size of packing)
209
Large quantity of silica gel is normally dried in a __________ dryer.
B. through circulation
210
For the same system, if the same liquid used in an absorber is decreased, the tower height will
A. increase
211
Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant.
A. agitated vessel
212
Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent
B. a binary mixture.
213
In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when
D. a total condenser is used.
214
In an interphase mass transfer process, the lesser the solubility of a given solute in a liquid, the higher are the chances that the transfer process will be
B. gas phase resistance controlled.
215
As the reflux ratio decreases, the
B. number of plates increases.
216
Which of the following equipments is not used for gas dispersion?
D. Spray towers
217
One mole feed of a binary mixture of a given composition is flash vaporised at a fixed P and T. If Raoult's law is obeyed, then changing the feed composition would effect
C. the fraction vaporised but not the product composition.
218
The equation, (I33, P12) is for
A. steady state equimolar counter diffusion
219
With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop
C. increases
220
The equation,(I35, P12) is for
B. stready state diffusion for stagnant case.
221
Which of these columns incurs the lowest pressure drop?
A. Packed column (with stacked packing)
222
In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase.
B. liquid
223
If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is
A. L/G
224
Which of the following remains constant during evaporative cooling process with recirculated water supply?
C. Wet bulb temperature
225
For stripping of a gas in a counter current stripper, the operating line
C. can lie above or below the equilibrium curve.
226
Which of the following same diameter columns gives lowest pressure drop per unit height?
C. Packed column (stacked)
227
Operating velocity in a packed tower is usually __________ the flooding velocity.
A. half
228
The Knudsen diffusivity is dependent on the
D. molecular velocity and por radius of the catalyst.
229
Minimum possible diameter of a packed coloumn is decided mainly by the
A. flooding
230
Solvent used in extractive distillation
B. forms a low boiling azeotrope.
231
The cooling effect in a cooling tower can be speeded up by
D. all (a), (b) and (c). (A. increasing the air velocity and area of exposed wet surface.) (B. reducing the barometric pressure.) (C. reducing the humidity of the air.)
232
The following plot gives the saturated humidity (He) versus temperature (T).Line joining (H1, T1) and (H2, T2) is the constant enthalpy line. Choose the correct one from among the alternatives A, B, C and D. (I50, P12)
D. T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.
233
When both the fluids flow concurrently in an absorber, the slope of the operating line is
A. - ve
234
The percentage humidity is less than the relative humidity only at __________ percent humidity.
C. both zero and hundred
235
Back-trapping in a distillation column
B. decreases tray efficiency.
236
Flooding in a vapor-liquid contacting equipment occurs in a tray, when the pressure drop through a tray is __________ the liquid head available in the downcomer.
B. more than
237
Milk is dried usually in a __________ dryer.
B. spray
238
At a given equilibrium pressure, with increase in temperature, the concentration of adsorbed gas on solid adsorbant
B. decreases
239
Which of the following adsorbent is used to decolourise yellow glycerine?
D. Activated carbon
240
Which of the following liquid temperature (T) Vs. vapor-gas mixture enthalpy (H) diagram is valid for humidification operation?
B. (I8, P13)
241
In a distillation column, with increase in the reflux ratio, the heat removed in the cooler
A. increases.
242
Pick out the wrong statement.
B. Relative volatility of a binary mixture changes appreciably with the minor change in temperature.
243
Which of the following is not a unit of mass transfer co-efficient?
D. None of these (A. Moles transferred/(time)(area)(mole fraction)) (B. Moles transferred/(time)(area)(pressure)) (C. Moles transferred/(time)(area)(mass A/mass B))
244
The falling rate period in the drying of a solid is characterised by
B. increasing temperatures both on the surface and within the solid.
245
In which of the following unit operations, the selectivity is an important parameter?
B. Solvent extraction
246
Which of the following is an undesirable characteristic for the solvent used in gas absorption?
D. None of these (A. Low vapor pressure) (B. Low viscosity) (C. High gas solubility)
247
Which of the following equipments is not used for liquid dispersion?
D. Agitated vessels
248
Diameter of raschig rings used in packed tower in industry is normally around __________ inches.
A. 2
249
The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is
C. 2.09 x 10-9
250
Pick out the wrong statement.
C. According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by sqrt(DAB)(b)P - 3, Q - 2
251
In case of non-ideal gases and liquids, the molal diffusivity
C. is independent of pressure.
252
Condensation of a vapour-gas mixture just begins, when (where, p = partial pressure of the vapour P = vapour pressure of the liquid)
A. p = P
253
__________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower.
C. Lewis
254
The expression, y(1 - x)/x(1 - y) is for
B. relative volatility
255
In physical terms, Schmidt number means
C. momentum diffusivity/mass diffusivity.
256
In case of liquids, the binary diffusivity is proportional to (where, T = temperature)
A. T
257
The diffusivity, DAB (for component A diffusing in B) is equal to the diffusivity DBA (for component B diffusing in A) for a binary mixture of
C. ideal gases
258
Mass transfer co-efficient is directly proportional to DAB0.5, according to __________ theory.
A. penetration
259
Sand is dried in foundaries in a___drier.
B. fluidised bed
260
Which of the following employs an accessory known as 'drift eliminator'?
B. Mechanical draft cooling tower.
261
Pick out the correct statement.
C. For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion.
262
Pick out the correct statement.
D. all (a), (b) and (c). (A. For identical gas flow rates, less pressure drop occurs through a plate tower than through a packed tower.) (B. Plate column can handle greater liquid loads without flooding than packed column, but the liquid hold up is more in the case of plate column.) (C. For the same duty, plate columns weigh less than packed columns.)
263
Humid volume is the total volume in m3 of 1 kg of
C. gas plus its accompanying vapour at 1 atm. and gas temperature.
264
Diameter to height ratio for a rashig ring is
A. 1
265
The equipment used in the extraction of highly corrosive radio active liquids is
A. pulse column
266
Advantage of continuous drying over batch drying is that the
D. all 'a', 'b' & 'c' (A. drying cost per unit weight of dried product is less.) (B. product with more uniform moisture content is produced.) (C. equipment size required is smaller.)
267
With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system)
A. increases
268
In a packed bed absorption column, the channelling will be noted by the
B. sharp drop in pressure drop.
269
Gaseous diffusivity at atmospheric pressure is of the order of __________ cm2/second.
A. 1
270
In liquid-liquid extraction, the number of phases at plait point is
A. 1
271
In a liquid-liquid extraction, 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X, where Y* is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer.
A. The entire amount of C is transferred to solvent B.
272
The surface renewal frequency in Danckwerts' model of mass transfer is given by (KL: mass transfer co-efficient)
A. sqrt(KL2.DA)
273
If Rm is the minimum reflux ratio, the optimum reflux ratio may be around __________ Rm.
A. 1.2 to 1.5
274
During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant.
A. wet bulb temperature
275
In case of absorption, both the operating and equilibrium lines will be straight for
C. dilute solutions and isothermal operation.
276
Mass transfer co-efficient varies as DAB0.5, according to the __________ theory.
B. surface renewal
277
For an absorber, both equilibrium and operating line will be straight for
C. dilute solution and isothermal operation.
278
A distillation column separates 10000 kg/hr of a benzene-toluene mixture as shown in the figure below: In the figure xF, xD and xW represent the weight fraction of benzene in the feed, distillate and residue respectively. The reflux ratio is (I46, P15)
B. 0.6
279
Unsaturated air (with dry bulb and wet bulb temperatures being 45°C and 25°C respectively) is passed through a water spray chamber maintained at 23°C. The air will be cooled and
A. humidified with wet bulb temperature decreasing.
280
Humid volume, at a given temperature is a/an __________ function of humidity.
C. linear
281
The Schmidt number which is defined as, μ/ρ D, is the ratio of the
A. momentum diffusivity to the mass diffusivity.
282
If f is defined as above, then which of the following applies to a feed at dew point ?
A. f = 1
283
Perforated plate towers are unique for solvent extraction because, they provide
C. repeated coalescence & redispersion of the drop phase.
284
In case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of __________ is zero.
A. interface
285
Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations.
C. Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.
286
The slope of the operating line for a single component co-current absorber when plotted in terms of mole ratio units is
C. (-) ve
287
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?
B. gas side
288
Pore size of the molecular seive 5A is __________ mm.
B. 0.5
289
Swenson-Walker crystalliser is a __________ unit
A. continuous
290
According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (αAB = 2) does not change appreciably in the coloumn.
C. 12
291
Absorption (liquid-gas system) with evolution of heat as compared to isothermal absorption results in
D. all (a), (b) and (c). (A. decreased solute solubility.) (B. large minimum liquid to gas (L/G) ratio.) (C. large number of trays.)
292
With increase in temperature, the mutual solubility of two liquids
A. increases
293
Pick out the wrong statement.
D. The capacity of a distillation coloumn is maximum at total reflux.
294
The relative volatility of a binary mixture at the azeotropic composition is
A. 1
295
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
D. Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.
296
Bound moisture is that liquid which exerts an equilibrium vapor pressure __________ that of the pure liquid at the given temperature.
A. less than
297
Lewis number (Le) is
A. Sc / Pr
298
Which of the following is not a continuous leaching equipment?
A. Pachuka tank
299
__________ extractor is used for the concentration of radioactive nuclear waste.
A. Pulsed column
300
Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture.
C. equilibrium
301
All moisture in a non-hygroscopic material is the __________ moisture.
C. unbound
302
Pick out the correct relationship. (where, Ri = internal reflux ratio Ro = external reflux ratio.)
A. (1 + Ro) = Ro/Ri
303
Separation of __________ employs gaseous diffusion process.
B. isotopes of uranium
304
For water-ethanol system, the minimum reflux ratio
A. is computed from the slope of the upper operating line that is tangent to the equilibrium curve.
305
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
306
Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysterisis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption.
A. lower than
307
Experimental determination of __________ is done by wetted wall column method.
B. mass transfer co-efficient
308
Pick out the wrong statement:
B. In case of a stripper, the equilibrium curve is always below the operating line.
309
In liquid extraction, if the selectivity is unity, then
B. no separation will occur.
310
Paper industry employs __________ driers.
A. cylinder
311
Pick out the wrong statement pertaining to the cooling towers.
D. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.
312
Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 x 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is
B. 8.5 x 10-4
313
Leaching of coarse solid lumps is also termed as
C. percolation
314
The main reason for dividing a tall packed tower into series of small towers is to
D. avoid channeling.
315
Co-current absorbers are usually used when the gas to be dissolved in the liquid is
C. a pure substance
316
At what percentage (by volume) of alcohol composition, it forms an azeotrope with water?
C. 95
317
Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ coloumn.
D. wetted wall
318
With the lowering of equiliDrium pressure, at a given temperature, the amount of ad-sorbate on the adsorbent
B. decreases.
319
Mass transfer co-efficient is defined as
B. Co-efficient = Flux/concentration difference.
320
When an unsaturated air-water mixture is heated at constant pressure, then
D. the relative humidity decreases.
321
At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent.
B. 0
322
In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is
B. equal to the heat of wetting.
323
Pick out the wrong statement:
D. The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.
324
The value of L/mG ratio for economical absorption operation ranges from
C. 1.25 to 2.0
325
Large scale usage of flash distillation is practised in
D. petroleum refinning
326
High pressure at the bottom of a distillation tower handling heat sensitive materials results in
A. thermal decomposition of bottoms.
327
Alcohol is dehydrated using __________ distillation.
B. azeotropic
328
Separation of two volatile liquids by distillation makes use of their
B. relative volatility
329
Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content.
B. tray
330
__________ is used as an 'entrainer' for the separation of acetic acid-water mixture by distillation.
C. Butyl acetate
331
Rotary dryers cannot handle __________ materials.
C. sticky
332
Pick out the correct statement.
D. none of these. (A. Diffusivity decreases with increase in temperature.) (B. Diffusivity increases with increase in molecular weight.) (C. Diffusivity increases with the size of the individual molecule.)
333
An example of elution is
A. separation of uranium oxide from its ore by H2SO4 in a Pachuca tank.
334
The operating line for an absorber is curved, when plotted in terms of
C. partial pressure
335
Relative volatility does not change appreciably with the change in
A. temperature
336
The dew point of a saturated gas phase equals the __________ temperature.
A. gas
337
A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process?
D. Temperature of the solid
338
In case of liquid-liquid binary diffusion, diffusivity of one constituent into another is not dependent on the
D. none of these
339
For continuous drying of grannular or crystalline material, the dryer used is the __________ dryer.
C. rotary
340
When adsorption hysteresis is observed, the desorption equilibrium pressure is __________ that obtained by adsorption.
A. always lower than
341
Moisture in a substance exerting an equilibrium vapour pressure less than that of pure liquid at the same temperature is called the __________ moisture.
A. bound
342
For a binary mixture with low relative volatility, continuous rectification to get pure products will require
D. high reflux ratio
343
Detergent solution is dried to a powder in a
A. spray dryer
344
Which of the following mixtures does not form an azeotrope at atmosheric pressure?
D. None of these (A. Water-alcohol) (B. Methyl alcohol-acetone) (C. Butyl acetate-water)
345
During bottling of cold drinks (e.g. Pepsi), the main resistance to mass transfer for the absorption of carbon dioxide in water lies in the
B. liquid film
346
The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by
A. increasing the gas film co-efficient.
347
Flooding results in
B. low tray efficiency
348
For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because
A. water has a high latent heat of evaporation.
349
In an operating distillation column, the
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.
350
The diffusivity (D) in a binary gas mixture is related to the temperature (T) as
C. D ∝ T^1.5
351
For which of the following unit operations, Lewis number is of significance?
D. Humidification
352
Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches.
B. 30
353
If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement.
D. none of these
354
The dimension of diffusivity is same as that of the
C. kinematic viscosity
355
The temperature to which a vapour gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature.
D. none of these
356
Entrainer used in azeotropic distillation should
A. form a low boiling azeotrope with one of the constituents of the mixture.
357
In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because
C. mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.
358
Pick out the wrong statement.
C. The operating pressure in solvent extraction system should be below vapor pressures of all components.
359
Leaching of coffee from coffee beans is done by
A. hot water
360
For contacting a highly soluble gas with a liquid
A. bubble the gas through liquid.
361
During drying operation, it is easier to remove the __________ moisture.
C. unbound
362
With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas
B. decreases
363
Ion exchange process is similar to
B. adsorption
364
A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state,
D. the top and bottom compositions correspond to the maximum enrichment available.
365
Dryer widely used in a textile industry is __________ dryer.
C. conveyor
366
Solvent used in extractive distillation
A. changes the relative volatility of the original components.
367
Air at a particular humidity is heated in a furnace. The new dew point
B. increases
368
The vapour pressure exerted by the moisture contained in a wet solid depends upon the
D. all (a), (b) and (c). (A. nature of the moisture.) (B. temperature.) (C. nature of the solid.)
369
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
370
Smoke is an example of
B. solid dispersed in gas
371
Which of the following adsorbant is used in the refinning of sugar?
A. Bone charcoal
372
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
373
Which of the following parameters remains constant during chemical dehumidification?
A. Dry bulb temperature
374
Drying of a solid involves __________ transfer.
C. both heat and mass
375
Mechanism of moisture removal in case of freeze drying of food stuff is by
B. sublimation
376
The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture.
B. temperature
377
Which is not concerned directly with mass transfer?
D. Froude number
378
Removal of __________ exemplifies an adsorption unit operation.
B. water from petrol
379
Can the efficiency of a plate in the distillation tower be greater than 100%?
C. Never
380
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.
A. increases
381
For gas absorption, low viscosity solvents are preferred, because of their
D. all (a), (b) and (c). (A. better flow characteristics.) (B. low pumping pressure drop.) (C. rapid absorption rates.)
382
To remove all the moisture from a wet solid it requires exposure to __________ air.
A. perfectly dry
383
The operating cost of a distillation column at minimum reflux ratio is
A. minimum
384
The reflux to a distillation column is 100 moles/hr, when the overhead product rate is 50 moles/hr. The reflux ratio is
A. 2
385
Molecular diffusivity of a liquid
A. increases with temperature.
386
The wet and 'dry bulb temperature for a vapour-gas mixture are 25°C and 30°C respectively. If the mixture is heated to 45°C at constant pressure, the wet bulb temperature will be __________ °C.
B. > 25
387
Henry's law states that the
A. partial pressure of a component over a solution is proportional to its mole fraction in the liquid.
388
Ammonia present in the coke oven gas is removed by washing with
B. dilute ammoniacal liquor
389
Which of the following processes is not an example of adsorption applied to gaseous separations?
D. Decolouration of yellow glycerene.
390
The critical moisture content in case of drying indicates the __________ rate period.
A. beginning of falling
391
Pick out the wrong statement
D. Relative saturation of unsaturated mixture of water vapor & air can not be increased by either reducing the mixture temperature or by increasing the total pressure.
392
According to Poiseuille's law, the permeability for gas flow through a capillary is proportional to (where, μ = gas viscosity)
B. 1/μ
393
For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be
A. 1
394
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
395
For the flow of gases through a capillary, with increase in temperature, the permeability __________ as per Knudsen law.
A. increases
396
Which of the following is directly concerned with psychrometry?
A. Lewis relationship
397
Plate efficiency in a distillation column is reduced due to the __________ of liquid.
D. all (a), (b) & (c) (A. entrainment) (B. foaming) (C. weeping & dumping)
398
The most efficient cooling tower out of the following is
A. induced draft
399
Sodium bicarbonate is produced during soda ash manufacture using a __________ tower.
B. baffle
400
Powdery materials can be guarded against caking tendency on storage by
D. none of these. (A. providing irregular grain size.) (B. providing minimum percentage of voids.) (C. having maximum possible points of contact.)
401
In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number.
A. Lewis
402
Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes?
D. Wetted wall columns
403
The temperature of water cooled in cooling tower is always __________ temperature of entering air.
A. more than the wet bulb
404
Which of the following processes is followed by unsaturated air (with dry bulb temperature 12°C and relative humidity 47%) passing through water spray washer (temperature of water being constant at 40°C?
C. Both heating and humidification
405
Mass transfer co-efficient is directly proportional to DAB according to the __________ theory.
A. film
406
The relative volatility of a binary mixture at constant temperature __________ the total pressure.
A. decreases with increase in
407
Tower diameter may be decreased by
B. use of increased tray spacing.
408
Rayleigh's equation applies to __________ distillation.
C. differential
409
Steady state equimolal counter diffusion is encountered in
A. separation of a binary mixture by distillation.
410
Polar organic compounds are normally used as separating agents for the azeotropic and extractive distillation. Which of the following is the most important factor to be considered for the choice of the separating agent for extractive distillation?
D. Selectivity
411
As the reflux ratio increases, the slope of the operating line for rectifying section
A. increases
412
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
413
The unit of volumetric diffusivity is
A. cm2/sec
414
For a ternery mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates.
D. pure component is represented by the apex.
415
Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the __________ temperature.
B. wet-bulb
416
The Reynolds number of the liquid was increased 100 fold for a laminar falling film used for gas-liquid contacting. Assuming penetrating theory is applicable, the fold increase in the mass transfer co-efficient (Kc) for the same sytem is
B. 10
417
The slope of 9-line is determined by the
C. thermal condition of the feed
418
In steam distillation, the
C. product must be immiscible with water.
419
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?
C. Wet bulb temperature
420
The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will
A. increase
421
Rose oil is extracted from rose leaves using __________ distillation.
D. steam
422
Hypersorption refers to a __________ process.
D. moving bed adsorption
423
Which of the following is the correct ternery diagram for liquid-liquid extraction system comprising of two pairs partly soluble (e.g., chlorobenzene-water-methyl ethyl ketone system)?
A. (I5, P22)
424
Extraction of coffee from its seed is done by
B. leaching.
425
In azeotropic mixture, the equilibrium vapour composition is
C. same as liquid composition.
426
With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux
B. decreases
427
Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of
B. thermal diffusivity to mass diffusivity.
428
According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity)
A. D
429
Dry bulb temperature of the gas is __________ the wet bulb temperature.
B. more than
430
Decoction refers to the use of solvent
B. at its boiling point
431
Flash distillation is suitable for separating the constituents of a binary system, which
B. have very wide boiling points.
432
The ratio of Murphree plate efficiency to point efficiency is 1 in a __________ flow model.
B. perfectly mixed
433
The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm2/sec.
A. 0.25
434
Flooding in a column results due to
A. high pressure drop
435
Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty?
C. Wetted wall tower
436
A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture?
A. The mixture exhibits an azeotrope at 101.3 kPa.
437
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
D. and dehumidified with decrease in wet bulb temperature.
438
The process employing desorption of the absorbed solute by a solvent is called
A. elution
439
Which of the following operations does not involve leaching?
D. Removing nicotine from its water solution by kerosene.
440
The recovery of pencillin from the acidified fermentation broth is done by
D. liquid extraction
441
Molecular seives are porous
C. synthetic zeolites crystals/metal alumino-silicates.
442
Calcium ammonium nitrate (a fertiliser) is dried in a __________ dryer.
A. rotary
443
A binary mixture of benzene and cyclohexane is separated by
B. extractive distillation
444
Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular difusion, if
D. there is equimolar counter diffusion.
445
Cox chart is useful in the design of
A. distillation column
446
Dew point of an air-water vapor mixture
D. all 'a', 'b' & 'c'. (A. decreases with decrease in pressure.) (B. at constant humidity & total pressure is fixed.) (C. corresponding to any point on the humidity chart is obtained by projecting a line through this point parallel to the temperature axis and to the saturation curve.)
447
Can a cooling tower cool water below the wet bulb temperature of inlet air?
B. no
448
The suitable evaporator for concentration of foaming liquids is a __________ evaporator.
A. long tube
449
The ratio of Murphree plate efficiency to point efficiency is always > 1 in a __________ flow model.
A. plug
450
Tea percolation employs
B. leaching
451
Which of the following assumes constant molal vaporisation and overflow?
A. McCabe-Thiele method
452
Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be
B. > 1
453
Selectivity of the solvent used in solvent extraction should be
B. > 1
454
Pick out the wrong statement pertaining to leaching.
A. Fine solids can not be leached in a Pachuka tank.
455
Wet bulb and dry bulb temperatures becomes identical at __________ percent saturation curve.
A. 100
456
NSc/NPr is called the
B. Lewis number
457
McCabe-Thiele method
A. uses molal units for material and energy balance.
458
The film penetration model of mass transfer was enunciated by
B. Toor and Marchello
459
The most economical range of absorption factor is
C. 1.25 to 2
460
Channelling is most severe
A. in towers packed with stacked packing.
461
Out of two equilibrium curves, first one lies above the diagonal and the second lies below the diagonal in the x-y plot. It means that separation by distillation is
C. more readily done in the second case compared to first one.
462
ADDUCTS' and 'CLATHRATES' are used in case of
B. crystallisation.
463
Adsorption is an unit operation which generally involves __________ systems.
C. fluid-solid
464
In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated.
C. extractive
465
Separation of the isotopes of helium for scientific investigations is done by
B. thermal diffusion
466
In a binary system, separation is very efficient, when the relative volatility is
B. > 1
467
Fenske-Underwood equation used for calculating the minimum number of theoretical plates in distillation column is valid for
D. all (a), (b) and (c) (A. constant molal overflow) (B. total reflux) (C. constant relative volatility)
468
The binary diffusivity in gases does not depend upon the
D. none of these
469
Berl saddle made of carbon cannot be used for
D. oxidising atmosphere
470
1 kg of a saturated aqueous solution of a highly soluble component A at 60°C is cooled to 25°C. The solubility limits of A are (0.6 kgA/kg water) at 60°C and (0.2 kgA/kg water) at 25°C. The amount in kg of the crystals formed is
C. 0.2
471
Priming in a distillation column
C. is characterised by the presence of foam throughout the space between trays.
472
The commonly used solvent in supercritical extraction is
D. carbon dioxide.
473
When the liquid over a plate is of uniform concentration, then
C. Murphree efficiency = point efficiency.
474
In saturated gas, the
A. vapour is in equilibrium with the liquid at the gas temperature.
475
As per Gilliland's equation, the diffusivity is
D. all 'a', 'b' & 'c' (A. directly proportional to 'T1.5'.) (B. inversely proportional to 'P'.) (C. dependent on the molecular volume & molecular weight of components.)
476
Pick out the wrong statement.
C. The operating line lies above the equilibrium curve in case of a gas desorber.
477
A mixture of 10% C6H6 vapour in air at 25°C and 750 mm Hg has a dew point of 20°C. Its dew point at 30°C and 700 mm Hg will be around __________ °C.
D. 18.7
478
Which of the following is not fixed by the process requirements, in the design of absorbers?
D. None of these.
479
If the amount of the steam used in steam distillation is increased, the temperature of distillation
B. decreases
480
Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the __________ moisture.
A. unbound
481
Inside the distillation columns, the
B. driving force for the liquid flow is its weight.
482
When the psychometric ratio is __________ then the adiabatic saturation temperature and wet bulb temperature becomes equal.
A. 1
483
Desirable value of absorption factor in an absorber is
C. > 1
484
Refractory bricks are usually dried in a __________ dryer.
B. tunnel
485
What is the degree of freedom of an absorption process in which only one component is transferred between phases?
A. 3
486
Sticky material can be dried in a __________ dryer.
A. tray
487
Langmuir equation is associated with
B. adsorption
488
During the constant rate period of drying of a solid,
C. surface evaporation of unbound moisture occurs.
489
At a fixed total pressure, humidity depends only on the
A. partial pressure of vapour in the mixture.
490
If moisture content of solid on dry basis is X, then the same on wet basis is
A. X/X+1
491
Flash distillation is
B. used for multicomponent systems like crude refining.
492
__________ developed the film theory.
A. Higbie
493
For absorbers, high pressure drop results in
C. high operating cost.
494
Which of the following parameters remains almost constant during adiabatic saturation of unsaturated air?
C. Wet bulb temperature
495
Coffee is prepared from coffee beans by leaching with
B. hot water
496
Gaseous diffusion co-efficient increases with increase in the
B. temperature
497
With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature)
A. increases
498
If xD = overhead product molal composition and RD = reflux ratio, then slope and intercept of the operating line for rectifying section are respectively
B. (I35, P26)
499
Pick out the wrong statement. Raoult's law does not apply, when the
C. component molecules are nonpolar.
500
Water-ethyl alcohal solution can be concentrated (in respect of alcohal concentration) by __________ distillation.
B. vacuum
501
L/mG is the expression for
A. absorption factor
502
Extraction of pencillin employs a __________ extraction coloumn.
A. centrifugal
503
In case of gases, the binary diffusivity is proportional to (where, P = pressure)
B. 1/P
504
When the gas to be dissolved in liquid is a/an __________ then normally co-current adsorber are used.
B. pure gas
505
Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the __________ number.
A. Schmidt
506
If a two phase system is in physical equilibrium; then it means that, the
D. all (a), (b) and (c)
(A. escaping tendency of each component from the liquid phase to the vapor phase is exactly equal to that from vapor phase to liquid phase.)
(B. temperature of the liquid phase is equal to that of the vapor phase.)
(C. total pressure throughout the liquid phase is equal to that throughout the vapor phase.)
507
McCabe-Thiele method of binary distillation does not assume that the
D. none of these
(A. sensible heat changes are negligible compared with latent heat changes.)
(B. molar latent heats of all components are equal.)
(C. heat of mixing is negligible.)
508
(NSh/NRe.NSc) is termed in mass transfer operation as the
A. Stanton number
509
The Hatta number is important in
D. gas absorption with chemical reaction.
510
When a multistage tray tower uses a minimum reflux ratio, it implies
B. infinite trays and minimum reboiler heat load.
511
CO2 can be absorbed by
B. heated charcoal
512
For the same process conditions, the reflux ratio of an unlagged distillation column
B. increases in winter
513
An ideal tower packing should not
D. hold up large amount of liquid in the packing.
514
Which of the following is a suitable absorbent for removal of H2S from natural gas?
B. Monoethanol amine (MEA)
515
Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (yin = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is, N+2 = 6 log (yin/yout).For 98% recovery of acetone, the number of trays required is/are
C. 9
515
Schimdt number and Lewis number for pure air at atmospheric conditions are respectively
A. < 1 and ≈ 1
515
"Below is given an equilibrium moisture curve of a substance. State which
regions represent free moisture and unbound moisture respectively. (I4, P27)"
A. II, III
516
Molecular diffusion is caused by the
B. thermal energy of the molecules.
517
At __________ reflux, theoretical number of plates in a distillation coloumn is calculated using Fenske-Underwood equation.
B. total
518
Separation of a mixture of two gases by absorption in the liquid solvent depends upon the difference in their
C. solubility
519
Components, having widely different boiling point in a binary mixture, can be separated using __________ distillation.
D. simple
520
Which of the following equipments is not used in liquid-liquid extraction?
A. Pachuka tank
521
Pick out the wrong statement.
C. Diameter of randomly packed tower is normally more than 1.2 metres.
521
Equilibrium-moisture curves of different solids
A. are different
522
Azeotropism for ethyl alcohol-water system disappears by
B. decreasing pressure
523
Degree of freedom for leaching and solvent extraction process is
B. 3
524
Diffusion co-efficient generally depends upon the temperature, pressure & the nature of the components of the system. Its dimension is not the same as that of the
A. mass transfer co-efficient.
524
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?
C. Bamboo
525
In the absorption of ammonia in water, the main resistance to absorption is by the __________ phase.
B. gas
526
Drying of refractory is normally carried out in a __________ dryer.
D. truck/tunnel.
526
A. differential distillation equation
527
Heat sensitive materials with very high latent heat of vaporisation may be economically separated using
A. liquid extraction
528
When the solvent dissolves very little of solute, then
C. large quantity of solvent is required to extract the solute.
529
An alkaline solution is used to reduce the concentration of carbon dioxide in a stream from 10% to 0.1% by absorption with irreversible chemical reaction. The overall number of transfer units based on gas phase is
B. 4.605
530
HETP is numerically equal to HTU, only when the operating line
C. and equilibrium lines are parallel.
531
"In a distillation operation, what is the effect of the temperature of the reflux stream (given below) on the condenser and reboiler loads ?
Reflux conditions:
(i) Reflux stream is completely liquid and is at its bubble point.
(ii) Reflux stream is below its bubble point."
D. Both condensor and reboiler loads are higher in case (ii) as compared to case (i).
532
Steady state equimolal counter diffusion occurs in case of
C. binary phase distillation
532
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
533
The relative saturation of an unsaturated mixture of gas and vapor is independent of the
D. none of these.
533
The adiabatic saturation curve for a vapour-gas mixture is
B. slightly concave upward.
534
Pick out the wrong statement.
D. Zirconia probe is used for the humidity measurement.
534
The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases 'A' and 'B' is
B. ∞
535
Drift in a cooling tower is
A. the water entrained by the circulating air.
536
With increase in the concentration of the adsorbate, the integral heat of adsorption
B. decreases.
537
Small dia distillation column can be a
A. packed column
538
If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is
B. 1
539
An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is
D. 0.152
539
__________ column is used in gas absorption process.
D. Packed
540
Nitrobenzene (boiling point = 210.6°C) is steam distilled at 1 atm pressure.Nitrobenzene will distill off __________ °C.
A. at < 100
541
Pick out the wrong statement.
D. Vanderwall adsorption is also called chemisorption.
542
At what value of reflux ratio, number of theoretical plates in a distillation column is minimum?
C. ∞
542
Batch tray dryers suffers from the disadvantage of
C. high labour cost & low heat economy.
543
In a moderately sized packed absorption tower, channeling (which is most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter
C. > 8:1
544
__________ column is preferred to be used, when a high liquid hold up is required in a reactor for gas-liquid reaction. B. Bubble
B. Bubble
545
Penetration model (theory) for mass transfer was enunciated by
C. Higbie
546
Surface renewal model of mass transfer was enunciated by
C. Danckwerts
547
When the __________ the relative humidity of air decreases, despite an increase in the absolute humidity.
A. temperature rises
548
For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as
C. Re^0.83
549
The relative humidity of air decreases in-spite of an increase in the absolute humidity, when the
A. temperature rises.
550
Unit of molal diffusivity is
C. gm moles/cm. sec
550
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.
551
Binary distillation involves the mass transfer by __________ at the gas-liquid interface.
D. a counter diffusion at an almost equal molar rate
552
In a gas-liquid absorption coloumn, for obtaining the maximum absorption efficiency
C. both gas as well as liquid streams should be distributed uniformly.
552
Reverse osmosis is also called
D. ultrafiltration.
553
Which of the following is not a batch drier?
C. Fluidised bed drier
553
Steam distillation is not recommended to be used, if the
A. azeotropic mixture is to be separated and the final product is miscible with water.
554
Rayleigh equation applies to __________ distillation.
A. differential
554
Mass transfer co-efficient 'K' according to penetration theory varies with mass dif-fusivity as
A. D^0.5
555
Most important factor to be considered in the selection of packings for absorbers is the __________ of packing.
C. porosity
555
__________ is the separation technique used for desalination of sea water.
B. Reverse osmosis
556
Danckwerts developed the __________ theory.
B. surface renewal
557
Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant
D. all (a), (b) & (c)
(A. humidity)
(B. velocity)
(C. temperature)
558
Which of the following provides maximum contact surface for a liquid-vapour system?
A. Packed tower
559
For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is
C. known
560
In stripping section of continuous distillation column, the
B. liquid is enriched with high boiler.
561
Molality is defined as the number of gm moles of solute per __________ of solvent.
C. Kg
562
__________ is concerned with the adsorption equilibria.
C. Freundlich equation
563
Which of the following is the correct ternery diagram for liquid-liquid extraction system comprising of one pair partly soluble (e.g. water-benzene-acetic acid in which A-diluent, B - solvent and C - solute)?
A. (I18, P30)
564
Fractional solvent extraction
B. employs two solvents
565
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
A. at ground level.
566
Raschig ring made of procelain cannot be used for treating concentrated
C. alkalis
567
H2S present in naphtha reformed gas is removed by absorbing with
A. ethanolamine
568
During constant rate drying period, vaporisation rate per unit drying surface area
C. does not change with time,
569
Pick out the wrong statement.
A. Mass transfer co-efficient does not account for gase-liquid diffusion.
570
In rectifying section of a continuous distillation column, the
B. vapour is enriched with high boilers.
571
For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams
A. increases
572
According to Chilton-Colburn analogy for mass transfer, NSt.NSc2/3 is equal to
B. f/2
573
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
C. 1.24
574
Minimum reflux ratio in a distillation column results in
C. maximum condenser size.
575
Flooding in a distillation column is detected by a sharp
D. increase in pressure drop.
576
In extraction, as the temperature increases, the area of hetrogeneity (area covered by binodal curve)
A. decreases
577
Pick out the wrong statement.
B. 1 Nm3 of dry air is lighter than 1Nm3 of humid air.
578
In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation.
A. lower than
579
At constant pressure, with increase of temperature, the dew point will
A. increase
580
For a single component absorber, the operating line is straight only when plotted in term of __________ units.
B. mole ratio
581
In case of unsaturated air
C. both (a) and (b)
(A. dew point < wet bulb temperature)
(B. wet bulb temperature < dry bulb temperature)
582
For a binary mixture with low relative volatility,
D. an azeotrope may be formed during distillation.
583
Plate efficiency
A. is a function of the mass transfer between liquid and vapour.
583
Absorption accompanied by heat evolution results in
C. decrease in equilibrium solubility.
584
Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the
B. high pressure drop of the gas.
585
For a distillation column operating at minimum reflux, the
C. number of plates required will be maximum.
586
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))
D. MXo ln(Xo/XF)
586
Flash distillation is suitable for the separation of components
C. having very wide boiling points.
587
In Mcabe-Thiele method, at infinite reflux ratio
C. both the operating lines coincide with the diagram.
587
587
Use of packed towers for distillation is generally limited to the
A. small sizes.
588
589
Which of the following decreases during evaporative cooling process with recirculated water supply?
D. None of these
(A. Wet bulb temperature)
(B. Relative humidity)
(C. Partial pressure of vapour)
590
Laboratory determination of the dif-fusivity of vapor is done by __________ method.
C. Winkel mann's
591
The minimum liquid rate to be used in an absorber corresponds to an operating line
C. tangential to the equilibrium curve
592
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
B. humidified
593
For absorbing a sparingly soluble gas in a liquid, the
B. liquid side coefficient should be increased.
594
A natural draft cooling tower is filled with wooden grids, which covers about __________ percent of the tower height.
A. 45580
595
The boiling points of pure components of a binary system __________ with increase in total pressure of the system.
B. increases
596
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
A. differential heat of adsorption.
597
Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as
B. K ∝sqrt(D)
598
Desulphurisation of petrol is done in a
B. rotating disc extractor
599
Chemisorption compared to physical absorption has
C. increased utilisation of stagnant zones of the liquid phase.
600
Rate of adsorption increases as the
B. temperature decreases.
601
Pick out the system with maximum boiling azeotrope at 1 atm.
A. acetone chloroform
602
At 750°K and 1 atm, the approximate value of Schmidt number for air is
B. 0.1
603
Calculation of mass transfer co-efficient is mostly/normally done using __________ theory.
B. film
604
The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if
B. NSc = NPr = NLe
605
For the gas absorption, the height of a transfer unit, based on the gas phase is given by (G: superficial molar gas velocity, L: superficial molar liquid velocity, FG:mass transfer co-efficient, mols/m2 , a: in-terfacial area per unit volume of tower)
A. G/FG.a
606
Which of the following is used for the concentration of rubber latex?
A. Agitated film evaporator
607
As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages
B. decrease
608
In triangular co-ordinates, the ternery composition point falls __________ of the triangle.
B. inside
609
In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raf-finate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg)
B. 8.89
610
Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)
C. (4De/πt)^1/2
611
Reboiler is considered as one theoretical plate, because
A. of the assumption that vapour and liquid leaving the reboiler are in equilibrium.
