mtn3 Flashcards by Marie Cruz

The Schmidt number which is defined as, μ/ρ D, is the ratio of
the
A. momentum diffusivity to the mass dif-fusivity.
B. thermal diffusivity to the mass diffusivity.
C. momentum diffusivity to the thermal diffusivity.
D. none of these.

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If f is defined as above, then which of the following applies to a
feed at dew point ?
A. f = 1
B. f < 1
C. f > 1
D. 0 < f < 1

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Perforated plate towers are unique for solvent extraction
because, they provide
A. higher contact area
B. better contact of the phase.
C. repeated coalescence & redispersion of the drop
phase.
D. none of these

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The slope of the operating line for a single component co-current
absorber when plotted in terms of mole ratio units is
A. 0
B. ∞
C. -ve
D. +ve

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Pick out the wrong statement pertaining to the analogy between
equations of heat and mass transfer operations.
A. Sherwood number in mass transfer is analogous to
Nusselt number in heat transfer.
B. Prandtl number in heat transfer is analogous to
Schmidt number in mass transfer.
C. Reynolds number in mass transfer is analogous to
Grashoff number in heat transfer.
D. Reynolds number remains the same in both heat and
mass transfer.

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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?
A. liquid side
B. gas side
C. interfacial
D. both liquid and gas side

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Pore size of the molecular seive 5A is __________ mm.
A. 5
B. 0.5
C. 0.05
D. 50

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Swenson-Walker crystalliser is a __________ unit
A. Continuous
B. Batch
C. semi-batch
D. cooling (adiabatic)-cum-evaporation

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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.
A. 5
B. 9
C. 12
D. 28

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Absorption (liquid-gas system) with evolution of heat as
compared to isothermal absorption results in
A. decreased solute solubility.
B. large minimum liquid to gas (L/G) ratio.
C. large number of trays.
D. all (a), (b) and (c).

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With increase in temperature, the mutual solubility of two liquids
A. increases
B. decreases
C. remains unchanged
D. decreases exponentially

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

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Separation of __________ employs gaseous diffusion process.
A. N2 and O2 from air
B. isotopes of uranium
C. isotopes of helium
D. SO2 and air

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Pick out the wrong statement.
A. In solvent extraction, the distribution co-efficient should
be as large as possible for solvent economy.
B. With increase in pressure, the solubility of gases in
solvent increases at a fixed temperature.
C. Decrease in Murphree plate efficiency is an indication
of entrainment in distillation coloumn.
D. The capacity of a distillation coloumn is maximum at
total reflux.

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The relative volatility of a binary mixture at the azeotropic
composition is
A. 1
B. > 1
C. 0
D. ∞

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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
A. only vapor phase follows Raoult’s law.
B. only liquid phase obeys Dalton’s law.
C. liquid phase obeys Dalton’s law and vapor phase
obeys Raoult’s law.
D. Vapor phase obeys Dalton’s law and liquid phase
obeys Raoult’s law.

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Bound moisture is that liquid which exerts an equilibrium vapor
pressure __________ that of the pure liquid at the given
temperature.
A. less than
B. more than
C. equal to
D. either (a) or (b); depends on the solid

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Lewis number (Le) is
A. Sc / Pr
B. Pr x St
C. Sh x Pr
D. St x Sh

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Which of the following is not a continuous leaching equipment?
A. Pachuka tank
B. Kennedy extractor
C. Bollman extractor
D. Hydrocyclones

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__________ extractor is used for the concentration of
radioactive nuclear waste.
A. Pulsed column
B. Seive plate
C. Mixer-settler
D. Ballman

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Moisture content of a substance when at equilibrium with a given
partial pressure of the vapour is called the __________
moisture.
A. Free
B. Unbound
C. Equilibrium
D. Bound

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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.
B. is computed from the intercept of the operating line.
C. cannot be computed.
D. is the optimum reflux ratio.

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All moisture in a non-hygroscopic material is the __________
moisture.
A. Free
B. Equilibrium
C. Unbound
D. Bound

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The interfacial area per unit volume of dispersion, in a gas-liquid
contactor, for fractional hold up of gas = 0.1 and gas bubble
diameter = 0.5 mm is given by (in m2/m3)
A. 500
B. 1200
C. 900
D. 800

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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 B. higher than C. same as D. either same or higher than

Experimental determination of __________ is done by wetted wall column method. A. diffusion co-efficient B. mass transfer co-efficient C. NTU D. none of these

Pick out the wrong statement: A. Absorption factor is constant, when the equilibrium and operating lines are straight. B. In case of a stripper, the equilibrium curve is always below the operating line. C. In case of an absorber, the operating line is always above the equilibrium curve. D. In the absorption of low solubility gases, the liquid film is the controlling resistance.

In liquid extraction, if the selectivity is unity, then A. separation of the constituents is the most effective. B. no separation will occur. C. amount of solvent required will be minimum. D. solvent flow rate should be very low.

Paper industry employs __________ driers. A. Cylinder B. Rotary C. Spray D. fluidised bed

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

Pick out the wrong statement: A. Change in barometric pressure does not affect the relative humidity. B. In case of a packed tower, the operating velocity is about half of the flooding velocity, generally. C. 'Elution' means the desorption of the adsorbed solute by a solvent. D. The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

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

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 A. 5.6 x 10-4 B. 8.5 x 10-4 C. 5.6 x 10-3 D. 8.5 x 10-3

Leaching of coarse solid lumps is also termed as A. Decoction B. Dissolution C. Percolation D. agitation and settling

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

Co-current absorbers are usually used when the gas to be dissolved in the liquid is A. sparingly soluble B. highly soluble C. a pure substance D. a mixture

At what percentage (by volume) of alcohol composition, it forms an azeotrope with water ? A. 90 B. 91.5 C. 95 D. 99

Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ coloumn. A. Spray B. Packed C. bubble cap plate D. wetted wall

With the lowering of equiliDrium pressure, at a given temperature, the amount of ad-sorbate on the adsorbent A. increases. B. decreases. C. remains same. D. either (a) or (b), depends on the system.

Mass transfer co-efficient is defined as A. Flux = Co-efficient/concentration difference. B. Co-efficient = Flux/concentration difference. C. Flux=concentration difference/co-effi-cient. D. none of these.

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

During sensible cooling process A. relative humidity decreases B. relative humidity increases C. wet bulb temperature decreases D. both (b) and (c)

At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent. A. 100 B. 0 C. 50 D. between 0 and 100

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

The value of L/mG ratio for economical absorption operation ranges from A. 0.5 to 0.8 B. 0.8 to 1.2 C. 1.25 to 2.0 D. 2.5 to 3.5

Large scale usage of flash distillation is practised in A. soap manufacturing B. ammonia synthesis plant C. polymerisation industry D. petroleum refining

High pressure at the bottom of a distillation tower handling heat sensitive materials results in A. thermal decomposition of bottoms. B. increased relative volatility. C. erosion of the tower. D. very efficient operation.

Alcohol is dehydrated using __________ distillation. A. Extractive B. Azeotropic C. Steam D. Molecular

Separation of two volatile liquids by distillation makes use of their A. Selectivity B. relative volatility C. solubility D. density difference

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

Which of the following increases during evaporative cooling process with recirculated water supply ? A. Wet bulb temperature B. Relative humidity C. Partial pressure of vapour D. Both (b) and (c)

Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content. A. Rotary B. Tray C. Freeze D. none of these

_________ is used as an 'entrainer' for the separation of acetic acid-water mixture by distillation. A. Furfural B. Benzol C. Butyl acetate D. Hexane

Rotary dryers cannot handle __________ materials. A. free flowing B. dry C. sticky D. granular

Pick out the correct statement. 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. D. none of these.

An example of elutioh is A. separation of uranium oxide from its ore by H2SO4 in a Pachuca tank. B. separation of sugar from sugar beet by hot water. C. dissolution of tannin out of tree barks by water. D. recovery of vegetable oils from seeds.

The operating line for an absorber is curved, when plotted in terms of A. mole fractions B. mole ratios C. partial pressure D. mass fractions

Relative volatility does not change appreciably with the change in A. temperature B. vapour pressure of either component C. total pressure D. none of these

Boiling point diagram is not affected by the ambient A. pressure B. humidity C. temperature D. both (b) and (c)

A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process ? A. Flow rate of inlet air B. Relative humidity of outlet air C. Humidity of inlet air D. Temperature of the solid

The dew point of a saturated gas phase equals the __________ temperature. A. Gas B. Room C. wet bulb D. none of these

In case of liquid-liquid binary diffusion, diffusivity of one constituent into another is not dependent on the A. temperature and pressure B. concentration C. nature of the constituents D. none of these

For continuous drying of grannular or crystalline material, the dryer used is the __________ dryer. A. Tunnel B. Tray C. Rotary D. none of these

When adsorption hysteresis is observed, the desorption equilibrium pressure is __________ that obtained by adsorption. A. always lower than B. always higher than C. same as D. dependent on the system; can be either lower or higher than

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

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

Detergent solution is dried to a powder in a A. spray dryer B. spouted bed dryer C. tunnel dryer D. pan open to atmosphere

Which of the following mixtures does not form an azeotrope at atmosheric pressure? A. Water-alcohol B. Methyl alcohol-acetone C. Butyl acetate-water D. None of these

Flooding results in A. high tray efficiency B. low tray efficiency C. high gas velocity D. good contact between the fluids

Ion exchange process is similar to A. absorption B. adsorption C. extraction D. leaching

For which of the following unit operations, Lewis number is of significance? A. Adsorption B. Binary distillation C. Gas absorption D. Humidification

Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches. A. 5 B. 30 C. 60 D. 100

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. B. increasing the liquid film co-efficient. C. increasing the total pressure. D. decreasing the total pressure.

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 B. Unbound C. Critical D. none of thes

For a binary mixture with low relative volatility, continuous rectification to get pure products will require A. low reflux ratio B. less number of trays C. small cross-section column D. high reflux ratio

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. B. Lewis number is close to unity. C. they are always equal under all circumstances. D. solubility of the components of air in water is very small.

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 A. gas film B. liquid film C. liquid-gas interface D. none of these

In a forced draft cooling tower, water is cooled from 95 to 80°F by exposure to air with a wet bulb temperature of 70°F. In this case, the A. range is 15°F. B. approach is 10°F. C. both (a) & (b). D. neither (a) nor (b).

Heat load in a cooling tower A. means the amount of heat thrown away (KCal/hr.) by the cooling tower. B. is equal to the number of kg, of water circulated times the cooling range. C. both (a) & (b). D. neither (a) nor (b)

The diffusivity (D) in a binary gas mixture is related to the temperature (T) as A. D ∝ T B. D ∝ T0.5 C. D ∝ T1.5 D. D ∝ T2

For which of the following unit operations, Lewis number is of significance? E. Adsorption F. Binary distillation G. Gas absorption H. Humidification

Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches. E. 5 F. 30 G. 60 H. 100

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. A. a1 = a2 B. a1 = 2a2 C. a1 = 0.5 a2 D. none of these

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

The temperature to which a vapour gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature. A. dew point B. wet bulb C. dry bulb D. none of these

Entrainer used in azeotropic distillation should A. form a low boiling azeotrope with one of the constituents of the mixture. B. form a new azeotrope of low relative volatility with one of the constituents of the mixture. C. have high latent heat of vaporisation. D. have high viscosity to provide high tray efficiency

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, A. composition of vapors and that of liquid do not vary throughout the column. B. reboiler load and condenser load are minimum C. the top and bottom compositions are unchanged with and without total reflux. D. the top and bottom compositions correspond to the maximum enrichment available.

With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas A. Increases B. Decreases C. decreases linearly D. remains unaffected

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because A. temperature is less. B. total pressure is less. C. mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition. D. saturated steam is used for steam distillation.

Pick out the wrong statement. A. The operating line always lies above the equilibrium solubility curve in case of a single component absorber. B. The operating line always lies below the equilibrium solubility curve in case of a single component stripper. C. The operating pressure in solvent extraction system should be below vapor pressures of all components. D. The solubility of a particular gas in ideal solution in any solvent is always the same.

Leaching of coffee from coffee beans is done by A. hot water B. hexane C. lime water D. dilute H2SO4 (hot)

For contacting a highly soluble gas with a liquid A. bubble the gas through liquid B. spray the liquid on gas stream C. either (a) or (b) would suffice. D. none of these.

During drying operation, it is easier to remove the _______ moisture. A. Equilibrium B. Critical C. Unbound D. Bound

Dryer widely used in a textile industry is __________ dryer. A. Festoon B. Cylinder C. Conveyor D. Tunnel

Solvent used in extractive distillation A. changes the relative volatility of the original components. B. should be of high volatility. C. should form azeotropes with the original components. D. all (a), (b) and (c)

Air at a particular humidity is heated in a furnace. The new dew point A. decreases B. increases C. depends on the extent of heating D. remain unchanged

The vapour pressure exerted by the moisture contained in a wet solid depends upon the A. nature of the moisture. B. temperature. C. nature of the solid. D. all (a), (b) and (c)

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

In a packed tower, the value of HETP equals HTUOG, when the equilibrium and the operating lines are (where, HETP = height equivalant to a theoretical plate HTUOG = overall gas phase height of a transfer unit) A. straight B. parallel C. both (a) & (b) D. neither (a) nor (b)

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

Which of the following adsorbant is used in the refinning of sugar ? A. Bone charcoal B. Wood charcoal C. Silica gel D. Activated clay

Stacked packing compared to dumped packing A. provides poorer contact between the fluids. B. gives lower pressure drop. C. both (a) and (b). D. gives higher pressure drop.

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

Which of the following parameters remains constant during chemical dehumidifica-tion? A. Dry bulb temperature B. Partial pressure of vapour C. Wet bulb temperature D. None of these

Drying of a solid involves __________ transfer. A. only heat B. only mass C. both heat and mass D. none of these

Mechanism of moisture removal in case of freeze drying of food stuff is by A. evaporation B. sublimation C. dehydration D. adsorption

The dew point of an unsaturated gas-vapor mixture does not depend upon the __________ of the mixture. A. Composition B. Temperature C. total pressure D. all (a), (b) and (c)

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. A. 25 B. > 25 C. < 25 D. – 25

Which is not concerned directly with mass transfer? A. Schmidt number B. Sherwood number C. Lewis relationship D. Froude number

Removal of _______ exemplifies an adsorption unit operation. A. uranium from its ore B. water from petrol C. ammonia from coke oven gas D. mustard oil from mustard seed

Can the efficiency of a plate in the distillation tower be greater than 100%? A. Yes B. Normally not; but is possible if infinite number of plates are put. C. Never D. Yes ; if the reflux ratio is maximum.

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 B. Decreases C. remains same D. increases linearly

For gas absorption, low viscosity solvents are preferred, because of their A. better flow characteristics. B. low pumping pressure drop. C. rapid absorption rates. D. all (a), (b) and (c).

To remove all the moisture from a wet solid it requires exposure to __________ air. A. perfectly dry B. highly humid C. high temperature D. none of these

The operating cost of a distillation column at minimum reflux ratio is A. minimum B. maximum C. infinite D. zero

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 B. 0.5 C. 50 D. 150

Molecular diffusivity of a liquid A. increases with temperature. B. decreases with temperature. C. may increase or decrease with temperature. D. is independent of temperature.

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 B. 0 C. 2 D. 3

Henry's law states that the A. partial pressure of a component over a solution is proportional to its mole fraction in the liquid. B. partial pressure of a component over a solution is proportional to the mole fraction in the vapour. C. vapour pressure is equal to the product of the mole fraction and total pressure. D. partial pressure is equal to the product of the mole fraction and total pressure.

Ammonia present in the coke oven gas is removed by washing with A. caustic solution B. dilute ammoniacal liquor C. dilute HCl D. ethanolamine

With increase in temperature, the leaching rate increases due to A. decreased liquid viscosity B. increased diffusivity C. both (a) and (b) D. neither (a) nor (b)

Which of the following processes is not an example of adsorption applied to gaseous separations? A. Recovery of valuable solvent vapors from dilute mixture with air and other gases. B. Dehumidification of air and gas. C. Removal of objectionable odour and impurities from industrial gases. D. Decolouration of yellow glycerene.

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

Pick out the wrong statement A. A horizontal line on the humidity chart indicates the temperature changes at constant molal humidity. B. When water is cooled from 80 to 70°C by exposure to the air with a wet bulb temperature of 60°C, then both the approach & the range would be 10°C. C. For unsaturated air-water vapor mixture at atmospheric conditions, the wet bulb temperature & adiabatic cooling lines are the same. 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.

According to Poiseuille's law, the permeability for gas flow through a capillary is proportional to (where, μ = gas viscosity) A. μ B. 1/μ C. √μ D. μ2

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 frac. in the gas side. The height of the tower (in m) corresponding to an operating line given by, y = 5x + 0.001 is A. 2.0 B. 1.56 C. 1.0 D. 0.56

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

For the flow of gases through a capillary, with increase in temperature, the permeability __________ as per Knudsen law. A. Increases B. Decreases C. remains same D. either (a) or (b); depends on the gas

Which of the following is directly concerned with psychrometry? A. Lewis relationship B. Galileo number C. Weber number D. Dean number

Plate efficiency in a distillation column is reduced due to the __________ of liquid. A. Entrainment B. Foaming C. weeping & dumping D. all (a), (b) & (c)

The most efficient cooling tower out of the following is A. induced draft B. forced draft C. natural draft D. atmospheric

Sodium bicarbonate is produced during soda ash manufacture using a __________ tower. A. Plate B. Baffle C. Packed D. none of these

Powdery materials can be guarded against caking tendency on storage by A. providing irregular grain size. B. providing minimum percentage of voids. C. having maximum possible points of contact. D. none of these.

In case of cooling towers, the ratio of the rates of heat and mass transfer is indicated by the __________ number. A. Lewis B. Grashoff C. Sherwood D. none of these

Which one of the following devices is not used for both the absorption as well as the liquid-liquid extraction processes ? A. Packed towers B. Plate towers C. Spray towers D. Wetted wall columns

For a ternary mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a __________ of the equilateral triangular co-ordinates. A. binary mixture is represented by the apex B. binary mixture is represented by any point inside C. ternary mixture is represented by the sides D. pure component is represented by the apex.

The temperature of water cooled in cooling tower is always __________ temperature of entering air. A. more than the wet bulb B. less than the wet bulb C. equal to the wet bulb D. equal to the dry bulb

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? A. Humidification only B. Heating only C. Both heating and humidification D. Evaporative cooling

Mass transfer co-efficient is directly proportional to DAB according to the __________ theory. A. Film B. Penetration C. surface-renewal D. none of these

The relative volatility of a binary mixture at constant temperature __________ the total pressure. A. decreases with increase in B. increases with increase in C. is independent of D. none of these

Tower diameter may be decreased by A. using higher reflux ratio. B. use of increased tray spacing. C. increasing the liquid flow rate. D. increasing the vapour flow rate.

Rayleigh's equation applies to __________ distillation. A. Continuous B. Steam C. Differential D. Flash

Steady state equimolal counter diffusion is encountered in A. separation of a binary mixture by distillation. B. absorption of NH3 from air by water. C. all liquid-liquid diffusion systems. D. all liquid-solid diffusion systems.

Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele's method ? A. Partial condenser B. Total condenser C. Reboiler D. Both (b) and (c)

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? A. Cost B. Availability C. Toxicity D. Selectivity

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

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

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

Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the __________ temperature. A. dry-bulb B. wet-bulb C. dew point D. adiabatic saturation

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 system is A. 100 B. 10 C. 5 D. 1

In steam distillation, the A. temperature is 100°C. B. temperature is more than 100° C. C. product must be immiscible with water. D. temperature is higher than the boiling point of either component.

In extraction, as the temperature increases, the area of hetrogeneity (area covered by binodal curve) A. decreases B. increases C. remains unchanged D. none of these

Pick out the wrong statement. A. The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr = 1. B. 1 Nm3 of dry air is lighter than 1Nm3 of humid air. C. The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity. D. An azeotropic mixture of two liquids has boiling point higher than either of them, when it shows negative deviation from Raoult's Law.

In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________ its relative saturation. A. lower than B. higher than C. equal to D. either (a) or (b), depends on the mixture composition

At constant pressure, with increase of temperature, the dew point will A. increase B. decrease C. remain unchanged D. increase/decrease ; depends on the temperature

For a single component absorber, the operating line is straight only when plotted in term of __________ units. A. partial pressure B. mole ratio C. mole fraction D. none of these

In case of unsaturated air A. dew point < wet bulb temperature B. wet bulb temperature < dry bulb temperature C. both (a) and (b) D. neither (a) not (b)

For a binary mixture with low relative volatility, A. use steam distillation. B. use molecular distillation. C. use high pressure distillation. D. an azeotrope may be formed during distillation.

Plate efficiency A. is a function of the mass transfer between liquid and vapour. B. increases due to foaming. C. increases due to liquid entrainment. D. increases due to weeping and dumping of liquid.

Absorption accompanied by heat evolution results in A. increased capacity of the absorber. B. increase in equilibrium solubility. C. decrease in equilibrium solubility. D. none of these.

For a distillation column operating at minimum reflux, the A. concentration of liquid and vapour leaving a plate will be same. B. reflux ratio will be maximum. C. number of plates required will be maximum. D. none of these.

Flash distillation is suitable for the separation of components A. having very close boiling points. B. which form maximum boiling azeotrope. C. having very wide boiling points. D. which form minimum boiling azeotrope.

In McCabe-Thiele method, at infinite reflux ratio A. number of plates is maximum. B. overhead product is maximum. C. both the operating lines coincide with the diagram. D. none of these.

Leaching rate is independent of the A. agitation B. temperature C. particle size D. none of these

Use of packed towers for distillation is generally limited to the A. small sizes. B. multicomponent distillation. C. high pressure operation. D. vacuum distillation.

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

Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the A. high evaporation losses of water. B. high pressure drop of the gas. C. difficulty in its fabrication. D. none of these.

Which of the following decreases during evaporative cooling process with recirculated water supply ? A. Wet bulb temperature B. Relative humidity C. Partial pressure of vapour D. None of these

Laboratory determination of the dif-fusivity of vapor is done by __________ method. A. wetted wall column B. Gilliland's C. Winkel mann's D. Wike's

The minimum liquid rate to be used in an absorber corresponds to an operating line A. of slope = 1 B. of slope = 0.1 C. tangential to the equilibrium curve D. none of these

Desulphurisation of petrol is done in a A. Bollman extractor B. rotating disc extractor C. packed extraction column D. plate type extraction column

For absorbing a sparingly soluble gas in a liquid, the A. gas side co-efficient should be increased. B. liquid side coefficient should be increased. C. gas side co-efficient should be decreased. D. liquid side co-efficient should be decreased.

Pick out the system with maximum boiling azeotrope at 1 atm. A. acetone chloroform B. ethyl alcohol-water C. benzene-ethyl alcohol D. none of these

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. B. heat of wetting. C. integral heat of adsorption. D. none of these.

Pick out the wrong statement. A. The binary diffusivity in liquids is of the order of 10-5 cm2 /sec. B. Molecular diffusion in solid is much faster than that in liquids. C. Particles movement from higher concentration to lower concentration takes place in diffusion process. D. According to Poiseuille's law, the permeability decreases with increase in tempe

Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as A. K ∝D B. K ∝√D C. K ∝D1.5 D. K ∝D2

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 A. cooled B. humidified C. both (a) & (b) D. dehumidified

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

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

A natural draft cooling tower is filled with wooden grids, which covers about _______ percent of the tower height. A. 10-15 B. 30-40 C. 70-80 D. 90-100

At 750°K and 1 atm, the approximate value of Schmidt number for air is A. 0.01 B. 0.1 C. 1 D. 10

The boiling points of pure components of a binary system __________ with increase in total pressure of the system. A. Decreases B. Increases C. remains unchanged D. may increase or decrease, depends on the system.

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. GFG∙a B. FGG∙a C. G∙aFG D. LFG∙G

Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time) A. (De.t)1/2 B. (De/t)1/2 C. (4De/πt)1/2 D. (4De/t)

Calculation of mass transfer co-efficient is mostly/normally done using __________ theory. A. surface renewal B. film C. penetration D. none of these.

The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if A. NSc = 1 B. NSc = NPr = NLe C. NPr = NLe D. NSc = NLe

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

As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages A. Increase B. Decrease C. remain unchanged D. can either increase or decrease, depends on the system

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

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) A. 6.89 B. 8.89 C. 10 D. 8.25

Reboiler is considered as one theoretical plate, because A. of the assumption that vapour and liquid leaving the reboiler are in equilibrium. B. vapour is recycled to the column. C. reboiler itself contains one plate. D. none of these.