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MASS TRANSFER
CONCEPTS
1.1 Mass transfer rate between two fluid phases does not necessarily depend on the ___ of the two phases. A. chemical properties B. physical properties C. degree of turbulence D. interfacial area
1.3 Fenske equation determines the A. maximum number of ideal plates. B. height of the distillation column. C. minimum number of theoretical plates. D. optimum reflux ratio.
1.5 Which of the following is the most suitable for extraction in a system having very low density difference? A. Mixer-settler extractor B. Centrifugal extractor C. Pulsed extractor D. Packed extraction twr
1.9 Fenske's equation for determining the minimum number of theoretical stages in distillation column holds good, when the A. relative volatility is reasonably constant. B. mixture (to be separated) shows negative deviation from ideality. C. mixture (to be separated) shows positive deviation from ideality. D. multicomponent distillation is involved.
1.12 __________ columns are used for liquid dispersion in a continuous gas phase. A. Packed B. Pulse C. Bubble cap D. Sieve plate
1.13 Overall efficiency of the distillation column is A. the ratio of number of ideal plates to actual plates. B. the ratio of number of actual plates to ideal plates. C. same as the Murphree efficiency. D. always more than the point efficiency.
1.16 Drying operation under vacuum is carried out to dry those materials which have very high unbound A. moisture content. B. reduce drying temperature. C. increase drying temperature. D. dry materials having high bound moisture content.
1.17 Air initially at 101. 3 kPa and 40°C and with a relative humidity of 50%, is cooled at constant pressure to 30°C. The cooled air has a A. higher dew point. B. higher absolute (specific) humidity. C. higher relative humidity D. higher wet bulb temperature.
1.18 Separation of two or more components of a liquid solution cannot be achieved by A. fractional crystallization B. liquid extraction C. absorption D. evaporation
1.20 At minimum reflux ratio for a given separation A. number of plates is zero. B. number of plates is infinity.
C. minimum number of the theoretical plates is required. D. separation is most efficient.
1.24 Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called A. latent heat B. humid heat C. specific heat D. sensible heat
1.30 In case of an absorber, the operating A. line always lies above the equilibrium curve. B. line always lies below the equilibrium curve. C. line can be either above or below the equilibrium curve. D. velocity is more than the loading velocity.
1.31 As the reflux ratio in a distillation column is increased from the minimum, the A. slope of the operating line in stripping section decreases. B. number of plates decreases very slowly first and then more and more rapidly. C. total cost first decreases and then increases. D. liquid flow increases while the vapor flow decreases for a system.
1.40 Which of the following unit operations makes use of Thiele-Geddes equation? A. Liquid-liquid extraction B. Solid-liquid extraction C. Multicomponent absorption with chemical reaction D. Multicomponent distillation.
1.41 Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty? A. Sieve plate column B. Bubble cap column C. Randomly packed column D. Wetted wall column
1.43 Chemisorption (chemical adsorption) is A. same as "Van der Waals" adsorption. B. characterised by adsorption of heat. C. an irreversible phenomenon. D. a reversible phenomenon.
1.46 In distillation columns, the number of bubble caps per tray primarily depends upon the A. allowable liquid velocity. B. allowable gas velocity. C. allowable gas and liquid velocities. D. feed composition.
1.47 In distillation, overhead product contains A. only one component B. two components C. any number of components D. only saturated liquid
2.2 Bollman extractor A. is a static bed leaching equipment. B. is used for extraction of oil from oilseed. C. is a centrifugal extractor. D. employs only counter-current extraction.
2.3 The relation, Sc = Pr = 1, is valid, when the mechanism of __________ transfer is same. A. heat and mass B. mass and momentum C. heat and momentum D. heat, momentum, mass
2.12 __________ diffusion is used for separating the isotopes of methane. A. Thermal B. Pressure C. Concentration D. Force
2.13 Ordinary diffusion process is also called ___ diffusion. A. pressure B. thermal C. concentration D. forced.
2.16 The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives A. low pressure drop and high hold up. B. high pressure drop and low hold up. C. low pressure drop and low hold up. D. high pressure drop and high hold up.
2.20 Weeping in a distillation column A. increases tray efficiency. B. provides large interfacial surface for mass transfer. C. results due to very high gas velocity. D. results due to very low gas velocity.
2.27 Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower. A. wetted wall B. bubble cap C. perforated tray D. packed
2.29 Free flowing granular materials can be best dried in a __________ drier. A. rotary B. cylinder C. drum D. freeze
2.34 The solvent used in liquid extraction should not have high latent heat of vaporisation, because A. the pressure drop and hence the pumping cost will be very high. B. it cannot be recovered by distillation. C. its recovery cost by distillation may be prohibitatively high. D. it will decompose while recovering by distillation.
2.41 Which of the following binary systems is an example of a maximum boiling azeotrope? A. Water-hydrochloric acid. B. Acetone-carbon disulphide. C. Water-ethyl alcohol. D. n-heptane-n-octane.
2.47 Very tall packed towers, divided into series of beds to A. reduce the overall pressure drop B. avoid channeling C. reduce liquid hold-up D. avoid flooding
2.48 Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture. A. unbound B. free C. critical D. bound
3.2 __________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids.
A. Wetted wall B. Packed C. Plate D. Spray
3.3 Deairation (removal of O2) of water is done by A. rectification B. absorption C. ion-exchange D. adsorption
3.10 The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are A. parallel B. straight C. both parallel and straight D. neither
3.12 ‘Absorption with chemical reaction' is involved in the removal of A. carbon dioxide from gaseous stream using alkaline solution. B. benzol from coke oven gas using solar oil/wash oil. C. ammonia from coke oven gas using refrigerated water. D. tar from coke oven gas in primary gas coolers using chilled water.
3.15 In paper industry, paper is dried in a ___dryer. A. tunnel B. heated cylinder C. conveyor D. festoon
3.20 Leaching of sugar from sugar beets is done by A. hot water B. hexane C. dilute H2SO4 D. lime water
3.21 Absorption factor method is used to calculate the number of ideal stages, when A. operating line lies above the equilibrium line. B. operating line lies below the equilibrium line. C. both operating and equilibrium lines are parallel. D. pressure drop in the column is very high.
3.24 If the solubilities of different components (in a liquid- liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that A. the system comprises of partially mis-cible liquids. B. the system comprises of miscible liquids. C. the system comprises of an azeotrope. D. on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.
3.29 The reciprocal of stripping factor is termed as A. selectivity index B. relative volatility C. absorption factor D. Murphree efficiency
3.33 In case of a desorber (stripper), the A. operating line always lies above the equilibrium curve. B. operating line always lies below the equilibrium curve. C. temperature remains unaffected. D. temperature always increases. 3.39 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.
5.15 In extractive distillation, solvent is A. added to alter the relative volatility of the mixture. B. of high volatility. C. present in overhead stream. D. of high viscosity to give high tray efficiency.
5.16 Radioactive nuclear waste is treated in A. mixer-settler extractor B. rotating-disc contactor C. pulsed column extractor D. Bollman extractor
5.17 Large scale drying of sugar is done in a ______ dryer. A. spouted bed B. tray C. rotary D. truck
5.21 A packed tower compared to a plate tower for a particular mass transfer operation A. incurs smaller pressure drop. B. allows installation of cooling coils. C. is less costly when built in large sizes/diameters. D. is more suitable, if suspended solids are present in fluid streams.
5.24 Large quantity of silica gel is normally dried in a __________ dryer. A. freeze B. through circulation C. rotary vacuum D. tray
5.26 Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant. A. agitated vessel B. sieve tray column C. bubble cap column D. packed tower
5.27 Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent A. a pure component. B. a binary mixture. C. a ternary mixture. D. partially miscible tern..
5.28 In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when A. saturated feed is not used. B. an azeotrope forms. C. the latent heat of vaporisation of the more and less volatile components are greatly different. D. a total condenser is used.
5.29 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 A. liquid phase resistance-controlled. B. gas phase resistance controlled. C. impossible. D. driven by a non-linear driving force.
5.31 Which of the following equipments is not used for gas dispersion? A. Agitated vessels B. Bubble cap tray towers C. Perforated sieve tray towers D. Spray towers
5.32 1 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 A. the product composition but not the fraction vaporised.
B. the product composition as well as the fraction vaporised. C. the fraction vaporised but not the product composition. D. neither the product composition nor the fraction vaporised.
5.36 Which of these columns incurs the lowest pressure drop? A. Packed column (with stacked packing) B. Packed column (with dumped packing) C. Bubble plate column D. Pulse column
5.40 For stripping of a gas in a counter current stripper, the operating line A. lies above the equilibrium curve. B. lies below the equilibrium curve. C. can lie above or below the equilibrium curve. D. is always parallel to the equilibrium curve.
5.41 Which of the following same diameter columns gives lowest pressure drop per unit height? A. Bubble-cap column B. Sieve-plate column C. Packed column (stacked) D. Randomly packed col..
5.45 The Knudsen diffusivity is dependent on the A. molecular velocity only. B. pore radius of the catalyst only. C. molecular mean free path only. D. molecular velocity and por radius of the catalyst.
5.46 Minimum possible diameter of a packed coloumn is decided mainly by the A. flooding B. gas viscosity C. liquid density D. liquid hold up
5.47 Solvent used in extractive distillation A. is of low volatility. B. forms a low boiling azeotrope. C. forms a high boiling azeotrope. D. does not alter the relative volatility of the original components.
6.5 Milk is dried usually in a __________ dryer. A. freeze B. spray C. tray D. rotary
6.7 Which of the following adsorbent is used to decolourise yellow glycerine? A. Silica gel B. Alumina C. Fuller's earth D. Activated carbon
6.15 Which of the following equipments is not used for liquid dispersion? A. Wetted wall towers B. Packed towers C. Venturi scrubbers D. Agitated vessels
6.19 In case of non-ideal gases and liquids, the molal diffusivity A. varies inversely as the pressure. B. varies directly as the pressure. C. is independent of pressure. D. is equal to the volumetric diffusivity.
6.25 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 A. Newtonion liquids B. non-Newtonion liquids C. ideal gases D. real gases
6.27 Sand is dried in foundaries in a___drier. A. rotary B. fluidisedbed C. vacuum D. spray
6.28 Which of the following employs an accessory known as 'drift eliminator'? A. Multiple effect evaporator. B. Mechanical draft cooling tower. C. Rotary dryer. D. Rotating disc contactor.
6.31 Humid volume is the total volume in m 3 of 1 kg of A. vapour laden gas at 1 atm. and room temperature. B. gas plus its accompanying vapour at 1 atm. and room temperature. C. gas plus its accompanying vapour at 1 atm. and gas temperature. D. vapour laden gas at 1 atm. and gas temperature.
6.33 The equipment used in the extraction of highly corrosive radio active liquids is A. pulse column B. spray column C. mixer settler D. baffle tower
6.45 For an absorber, both equilibrium and operating line will be straight for A. concentrated solution and non-isothermal operation. B. dilute solution and non-isothermal operation. C. dilute solution and isothermal operation. D. concentrated solution and isothermal operation.
6.48 Humid volume, at a given temperature is a/an __________ function of humidity. A. inverse B. exponential C. linear D. logarithmic
7.5 The individual mass transfer co-efficients (moles/m^2. 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
7.7 Swenson-Walker crystalliser is a __________ unit A. continuous B. batch C. cooling (adiabatic)-cum-evap. D. semi-batch
7.16 Which of the following is not a continuous leaching equipment? A. Pachuka tank B. Kennedy extractor C. Bollman extractor D. Hydrocyclones
7.17 __________ extractor is used for the concentration of radioactive nuclear waste. A. Pulsed column B. Seive plate
C. Mixer-settler D. Ballman
7.18 Moisture content of a substance when at equilibrium with a given partial pressure of vapour is called __ moisture. A. free B. unbound C. equilibrium D. bound
7.19 All moisture in non-hygroscopic material is __moisture. A. free B. equilibrium C. unbound D. bound
7.21 Separation of __________ employs gaseous diffusion process. A. N 2 and O 2 from air B. isotopes of uranium C. isotopes of helium D. SO 2 and air
7.22 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.
7.27 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.
7.28 Paper industry employs __________ driers. A. cylinder B. rotary C. spray D. fluidised bed
7.32 Leaching of coarse solid lumps is also termed as A. decoction B. dissolution C. percolation D. agitation and settling
7.33 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.
7.34 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
7.36 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
7.42 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.
7.45 Large scale usage of flash distillation is practised in A. soap manufacturing B. ammonia synthesis plant C. polymerisation industry
C. Silica gel D. Activated clay
9.3 Mechanism of moisture removal in case of freeze drying of food stuff is by A. evaporation B. sublimation C. dehydration D. adsorption
9.5 Which is not concerned directly with mass transfer? A. Schmidt number B. Sherwood number C. Lewis relationship D. Froude number
9.6 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
9.7 Can the efficiency of a plate in the distillation tower be greater than 100%? A. Yes B. Normally not; but is possible if C. Never D. Yes; if reflux ratio is maximum.
9.16 Ammonia present in the coke oven gas is removed by washing with A. caustic solution B. dilute ammoniacal liquor C. dilute HCl D. ethanolamine
9.18 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.
9.26 Which of the following is directly concerned with psychrometry? A. Lewis relationship B. Galileo number C. Weber number D. Dean number
9.28 The most efficient cooling tower out of the following is A. induced draft B. forced draft C. natural draft D. atmospheric
9.31 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
9.32 Which one of the following devices is not used for both the absorption as well as liquid-liquid extraction processes? A. Packed towers B. Plate towers C. Spray towers D. Wetted wall columns
9.34 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 & humidifica D. Evaporative cooling
9.35 Mass transfer co-efficient is directly proportional to D AB according to the __________ theory. A. film B. penetration C. surface-renewal D. none of these
9.38 Rayleigh's equation applies to __________ distillation. A. continuous B. steam C. differential D. flash
9.39 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.
9.41 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
9.45 For a ternery 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. ternery mixture is represented by the sides D. pure component is represented by the apex.
9.46 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
9.48 The slope of 9-line is determined by the A. reflux ratio B. plate efficiency to be achieved C. thermal condition of the feed D. relative volatility.
9.49 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.
10.3 Rose oil is extractd from rose leaves using _ dstllation. A. high pressure B. low pressure C. extractive D. steam
10.4 Hypersorption refers to a __________ process. A. fixed bed absorption B. moving bed absorption C. fixed bed adsorption D. moving bed adsorption
10.6 Extraction of coffee from its seed is done by A. liquid-liquid extraction. B. leaching. C. extractive distillation. D. steam distillation.
10.13 Flash distillation is suitable for separating the constituents of a binary system, which A. form minimum boiling azeotrope. B. have very wide boiling points. C. have very close boiling points. D. form constant boiling azeotrope.
10.16 Flooding in a column results due to A. high pressure drop B. low pressure drop C. low velocity of the liquid D. high temperature
10.17 Which of the following gas-liquid contacting devices incurs the least pressure drop for a particular duty? A. Grid tray tower B. Perforated tray tower C. Wetted wall tower D. Bubble cap tower
The composition of the mixture, in percent by volume is: o- xylene 30, p-xylene 60. and m-xylene 10. 10.19 Unsaturated air (with dry bulb temp. & dew point being 35°C & 18°C respectively) is passed through a water spray chamber maintained at 15°C. the air will be cooled A. and humidified. B. and dehumidified with increase in wet bulb temperature. C. at the same relative humidity. D. and dehumidified with decrease in wet bulb temperature.
10.20 The process employing desorption of the absorbed solute by a solvent is called A. elution B. osmosis C. reverse osmosis D. sublimation
10.22 Which of the following operations does not involve leaching? A. Dissolving gold from ores. B. Dissolving pharmaceutical products from bark or roots. C. Dissolving sugar from the cells of the beet. D. Removing nicotine from its water solution by kerosene.
10.23 The recovery of pencillin from the acidified fermentation broth is done by A. distillation B. evaporation C. absorption D. liquid extraction
10.26 Calcium ammonium nitrate (a fertiliser) is dried in a __________ dryer. A. rotary B. vacuum C. tunnel D. tray
10.27 A binary mixture of benzene and cyclohexane is separated by A. flash vaporization B. extractive distillation C. solvent extraction D. ordinary distillation
10.28 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 A. mass transfer is accompanied by reaction. B. diffusion of A is in stagnant medium B. C. molecular mean free path is high. D. there is equimolar counter diffusion.
10.29 Cox chart is useful in the design of
A. distillation column B. evaporator C. dryer D. crystallizer
10.33 The suitable evaporator for concentration of foaming liquids is a __________ evaporator. A. long tube B. short tube C. vacuum D. falling film
10.45 Channeling is most severe A. in towers packed with stacked packing. B. in towers packed randomly with crushed solids. C. in dumped packing of regular units. D. at very high liquid flow rate.
10.47 'ADDUCTS' and 'CLATHRATES' are used in case of A. extractive distillation. B. crystallisation. C. absorption. D. none of these.
10.48 Adsorption is an unit operation which generally involves __________ systems. A. liquid-solid B. gas-solid C. fluid-solid D. Solid-solid
10.49 In case of __________ distillation, a solvent is added to alter the relative volatility of the mixture to be separated. A. molecular B. azeotropic C. extractive D. flash.
10.50 Separation of the isotopes of helium for scientific investigations is done by A. reverse osmosis B. thermal diffusion C. leaching D. solvent extraction
11.4 Berl saddle made of carbon cannot be used for A. alkalis B. SO 2 C. H 2 SO 4 D. oxidising atmosphere
11.7 Priming in a distillation column A. results from very low gas velocity. B. is desirable from point efficiency consideration. C. is characterised by the presence of foam throughout the space between trays. D. reduces the overall pressure drop.
11.8 Commonly used solvent in supercritical extraction is A. methyl ethyl ketone. B. water. C. carbon tetrachloride. D. carbon dioxide.
11.16 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 B. critical C. free D. bound
11.20 Refractory bricks are usually dried in a ______ dryer. A. tray B. tunnel C. conveyor D. feston
11.32 Coffee is prepared from coffee beans by leaching with A. cold water B. hot water C. dilute hot caustic solution D. naphtha
11.41 When the gas to be dissolved in liquid is a/an __________ then normally co-current adsorber are used. A. mixture of two gases B. pure gas C. ideal gas D. sparingly soluble gas
13.1 In a gas-liquid absorption coloumn, for obtaining the maximum absorption efficiency A. liquid stream should be distributed uniformly. B. gas stream should be distributed uniformly. C. both gas as well as liquid streams should be distributed uniformly. D. by passing should be completely avoided.
13.2 Reverse osmosis is also called A. dialysis B. electrodilysis C. diffusion D. ultrafiltration.
13.3 Which of the following is not a batch drier? A. Truck drier B. Agitated pan drier C. Fluidised bed drier D. Vacuum shelf drier
13.4 Steam distillation is not recommended to be used, if A. azeotropic mixture is to be separated and the final product is miscible with water. B. liquids decompose, if distilled directly at atmospheric pressure. C. material cannot be distilled by indirect heating even under low pressure, because of the high boiling temperature. D. material to be distilled is thermally unstable or has the tendency to react with other components associated with it, at the boiling temperature.
13.7 Most important factor to be considered in the selection of packings for absorbers is the __________ of packing. A. size B. durability C. porosity D. cost
13.8 __________ is the separation technique used for desalination of sea water. A. Thermal diffusion B. Reverse osmosis C. Adsorption D. absorption
13.13 Which of the following provides maximum contact surface for a liquid-vapour system? A. Packed tower B. Bubble-cap plate column C. Seive-plate column D. Wetted wall column
13.5 Rayleigh equation applies to __________ distillation. A. differential B. flash C. equilibrium D. molecular
13.14 For experimental determination of mass transfer co- efficient by wetted wall tower, the mass transfer area is A. calculated B. unknown C. known D. not rqd
13.21 Raschig ring made of procelain cannot be used for treating concentrated A. hydrochloric acid B. nitric acid C. alkalis D. sulphuric acid
13.22 H 2 S present in naphtha reformed gas is removed by absorbing with A. ethanolamine B. K 2 CO 3 C. HCl D. vacuum gas oil
13.29 Minimum reflux ratio in a distillation column results in A. optimum number of trays. B. minimum reboiler size. C. maximum condenser size. D. minimum no. of trays
13.37 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.
13.43 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.
13.46 Use of packed towers for distillation is generally limited to the A. small sizes. B. multicomponent distillat C. high pressure operation. D. vacuum distillation.
13.49 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
14.2 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.
14.7 Desulphurisation of petrol is done in a A. Bollman extractor B. rotating disc extractor C. packed extraction column D. plate type extraction column
14.15 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
CORRECT OR WRONG STATEMENT
12.28 Pick out the wrong statement. D. Zirconia probe is used for the humidity measurement.
12.37 Pick out the wrong statement. D. Vanderwall adsorption is also called chemisorption.
13.24 Pick out the wrong statement. A. Mass transfer co-efficient does not account for gas- liquid diffusion.
13.32 Pick out the wrong statement. B. 1 Nm^3 of dry air is lighter than 1Nm^3 of humid air.
13.47 Pick out the wrong statement. B. Molecular diffusion in solid is much faster than that in liquids.
FORMULAS, NUMBER, AND LAWS
1.29 Which of the following plays an important role in problems of simultaneous heat and mass transfer? A. Lewis number B. Schmidt number C. Prandtl number D. Sherwood number
1.32 Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve) A. S2/S1 B. S1/S2 C. S1 - S2 D. S1xS
1.45 Raoult's law applies to the A. all liquid solutions B. non-ideal solution only. C. non-volatile solute. D. solvents.
1.50 Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as A. K ∝ D B. K ∝D C. K ∝ D^1.5 D. K∝D^
2.1 The McCabe Δ L law states that the A. molar heats of vaporisation of components are nearly equal. B. linear crystal growth rate depends on the degree of supersaturation. C. linear crystal growth rate does not depend on the crystal size. D. linear crystal growth rate depends on the crystal size.
2.7 When the liquid phase and vapour phase of a binary system obeys Raoult's and Dalton's law respectively, the relative volatility is the ratio of A. vapour pressure of component A to that of component B. B. vapour pressure of component A to the total pressure. C. vapour pressure of component A to the partial pressure of A. D. partial pressure of component A to the total pressure.
2.19 Raoult's law is applicable to the A. ideal solutions B. real solutions C. mixture of water and alcohol D. non-ideal gases
2.31 Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number. A. Sherwood B. Schmidt C. Peclet D. Stanton
2.40 The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law. A. exponential B. parabolic C. linear D. cubic 2.42 (NRe. NSc) is termed in mass transfer operation as the __________ number. A. Stanton B. Sherwood C. Peclet D. none of these
2.43 The binary diffusivity in gases and liquids vary respectively as A. T^3/2 and T B. T and T^3/ C. T and T^3/2 D. T^3/2 and T
3.7 Which of the following solutions will follow Raoult's law most closely? A. A solution of benzene, toluene and oxylene. B. 35% solution of camphor in water. C. 35% solution of NH3 in water. D. A solution of polar organic compounds (not of homologs of a series).
3.23 If f = moles of vapour present per mole of feed, then the slope of feed line is (Mcabe-Thiele method) A. (1-f)/f B. –(f-1)/f C. -1/f D. -f/(1-f)
3.30 Ponchan-Savarit method analyses the fractional equipment based on A. enthalpy balance only. B. material balance only. C. both enthalpy and material balances. D. the assumption of constant molaloverflow.
4.4 Freundlich equation applies to the adsorption of solute from A. dilute solutions, over a small concentration range. B. gaseous solutions at high pressure. C. concentrated solutions. D. None of these.
4.7 The diffusivity (D) in a binary gas mixture is related to the pressure (P) as C. D ∝ 1/P
4.18 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 A. T^1/2 B. T C. T^2 D. T^
4.31 The Kundsen diffusivity is proportional to (where, T = absolute temperature) A. T^1/2 B. T^2 C. T D. T^
4.34 The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.) A. Kc = Kp = Km B. Kc = Kp / RT = Km. RT / P C. Kc = Kp****. RT = Km****. RT / p D. none of these
4.47 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 A. D/a B. D/2a C. proportional to D^1/ D. dependent on the Reynolds number
4.50 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)
9.21 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. μ^2
9.43 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
9.44 The unit of volumetric diffusivity is A. cm^2 /sec B. cm/sec C. cm^3 /sec D. cm^2 /sec 2
10.5 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)?
10.9 Lewis number, which is important in problems involving simultaneous heat and mass transfer, is ratio of A. mass diffusivity to momentum diffusivity. B. thermal diffusivity to mass diffusivity. C. momentum diffusivity to thermal diffusivity. D. none of these.
10.10 According to the film theory of mass transfer, the mass transfer co-efficient is proportional to (where, D = molecular diffusivity) A. D B. D^2 C. D0.5^ D. 1/D
10.36 Which of the following assumes constant molal vaporisation and overflow? A. McCabe-Thiele method B. Ponchan-Savarit method C. Enthalpy concentration method D. Plate absorption column
10.41 NSc / NPr is called the A. psychrometric ratio B. Lewis number C. Sherwood number D. Stantan number
10.42 McCabe-Thiele method A. uses molal units for material and energy balance. B. uses weight fractions to express liquid and vapour composition. C. can use any type of units. D. is more accurate than Ponchan-Savarit method.
10.43 The film penetration model of mass transfer was enunciated by A. Gilliland B. Toor and Marchello C. Stefan D. Fick
11.9 When the liquid over a plate is of uniform concentration, then A. Murphree efficiency > point efficiency.
B. Murphree efficiency < point efficiency. C. Murphree efficiency = point efficiency. D. Murphree efficiency ≠ point efficiency.
11.24 Langmuir equation is associated with A. leaching B. adsorption C. steam distillation D. multicomponent absorption.
11.27 If moisture content of solid on dry basis is X, then the same on wet basis is
11.29 __________ developed the film theory. A. Higbie B. Fick C. Ergun D. Levenspeil
11.35 If x (^) D = overhead product molal composition and RD = reflux ratio, then slope and intercept of the operating line for rectifying section are respectively
11.38 L / mG is the expression for A. absorption factor B. Brinkman number C. slope of operating line in absorber D. slope of operating line in stripper.
11.40 In case of gases, the binary diffusivity is proportional to (where, P = pressure) A. P B. 1/P C. 1/√P D. √P
11.42 Corresponding to Prandtl number in heat transfer, the dimensionless group in mass transfer is the _____ number. A. Schmidt B. Sherwood C. Peclet D. Stanton
11.45 ( NSh / NRe. NSc ) is termed in mass transfer operation as A. Stanton number B. Peclet number C. thermal diffusivity D. momentum diffusivity
11.46 The Hatta number is important in A. multicomponent distillation. B. binary distillation. C. gas absorption without chemical reaction. D. gas absorption with chemical reaction.
12.6 At _ reflux, theoretical number of plates in a distillation coloumn is calculated using Fenske-Underwood equation. A. operating B. total C. minimum D. maximum permissible
12.18 The expression, ln( F / W ) = is A. differential distillation equation B. for NtoG in absorption for dilute mixture C. slope of q -line in McCabe-Thiele method D. for relative volatility
12.22 HETP is numerically equal to HTU, only when the operating line A. lies below the equilibrium line.
B. lies above the equilibrium line. C. and equilibrium lines are parallel. D. is far from the equilibrium line. 12.25 J D factor for mass transfer is a function of Reynolds number. Mass transfer by molecular diffusion from a single drop to surrounding still air is given by A. Nsh = 2 B. Nst = 2 C. Nsc = 2 D. none
12.46 For turbulent mass transfer in pipes, the Sherwood number depends on the Reynolds number as A. Re0.33^ B. Re0.53^ C. Re0.83^ D. Re
12.48 Unit of molal diffusivity is A. cm^2 /sec gm. mole B. gm moles/cm^2. sec C. gm moles/cm. sec D. gm moles/cm^2. Sec
13.6 Mass transfer co-efficient ' K ' according to penetration theory varies with mass dif-fusivity as A. D0.5^ B. D C. 1/D D. D1.
13.10 Danckwerts developed the __________ theory. A. penetration B. surface renewal C. film D. none of these
13.17 _______ is concerned with the adsorption equilibria. A. Fick's law B. Gibb's equation C. Freundlich equation D. none of these
13.18 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)?
13.27 According to Chilton-Colburn analogy for mass transfer, NSt. NSc 2/3^ is equal to A. f B. f/2 C. 2f D. 1/f
13.42 A solid is being dried in the linear drying rate regime from moisture content Xo to XF. 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 )
13.44 In Mcabe-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. 14.6 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 ∝D^2
14.12 Calculation of mass transfer co-efficient is mostly/normally done using __________ theory. A. surface renewal B. film C. penetration D. none of these.
14.13 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
14.14 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/m^2 , a : in-terfacial area per unit volume of tower)
14.19 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. (4 De /π t ) 1/2^ D. (4 De / t )
1 or 0, +VE/-VE, VALUES
13.20 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. B. 2 metres above the ground. C. 5 metres above ground. D. 10 metres above ground.
14.3 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-
14.11 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
PROBLEM SOLVING
13.28 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 A. 0.54 B. 1.04 C. 1.24 D. 1.
14.18 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 x (^) f = 0.2. The mixture splits into an extract phase E and a raf-finate phase R containing A at x B = 0.5 and x R = 0. respectively. The total mass of the extract phase is (in Kg) A. 6.89 B. 8.89 C. 10 D. 8.
5.13 In a counter-current extractor, as the axial mixing increases, the extraction efficiency A. increases B. decreases C. remains unchanged D. Depends on the P
5.25 For the same system, if the same liquid used in an absorber is decreased, the tower height will A. increase B. decrease C. remain unaffected D. decrease or increase
5.34 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 A. decreases B. remains unchanged C. increases D. dec exponentially
5.44 Operating velocity in a packed tower is usually __________ the flooding velocity. A. half B. twice C. equal to D. more than
6.3 Back-trapping in a distillation column A. increases tray efficiency. B. decreases tray eff. C. reduces pressure drop. D. is desirable
6.4 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. A. less than B. more than C. same as D. very much less
6.6 At a given equilibrium pressure, with increase in temp., the concentration of adsorbed gas on solid adsorbant A. increases B. decreases C. remains unchanged D. increases exponentially
6.9 In a distillation column, with increase in the reflux ratio, the heat removed in the cooler A. increases. B. decreases. C. remains unaffected. D. and the heat required in
6.35 With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system) A. increases B. decreases C. remains unaffected D. increases Linearly 6.36 In a packed bed absorption column, the channelling will be noted by the A. increase in flow rate. B. sharp drop in pressure drop. C. sharp rise in pressure drop. D. none of these.
7.10 With increase in temperature, the mutual solubility of two liquids A. increases B. decreases C. remains unchanged D. decrease exponentially
7.24 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
7.39 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.
8.12 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 system
8.21 The overall mass transfer co-efficient for the absorption of SO 2 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.
8.33 In case of steam distillation, the steam leaving 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. 8.32 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.
8.38 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
8.43 Air at a particular humidity is heated in a furnace. The new dew point A. decreases B. increases C. depends on the extent D. remain unchanged
9.8 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
9.13 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.
9.33 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
9.36 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
9.37 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.
9.42 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
10.2 The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, number of ideal stages will A. increase B. decrease C. remains same D. depend on saturated boiling poi
10.7 In azeotropic mixture, the equilibrium vapour composition is A. more than liquid composition. B. less than liquid composition. C. same as liquid composition. D. independent of pressure.
10.8 With lapse of time, the overhead composition of light component in case of batch distillation with constant reflux A. increases B. decreases C. remains same D. may increase or decrease
10.11 Dry bulb temperature of the gas is __________ the wet bulb temperature. A. less than B. more than C. equal to D. none of these
11.15 If the amount of the steam used in steam distillation is increased, the temperature of distillation A. increases B. decreases C. remains unchanged D. depends on relative volatility
11.30 For absorbers, high pressure drop results in A. increased efficiency. B. decreased efficiency. C. high operating cost. D. better gas liquid contac
11.34 With increase in absolute humidity, the dew point of an unsaturated mixture of air and water vapor (at constant pressure and temperature) A. increases B. remains unchanged C. decreases D. decreases linearly
12.12 Azeotropism for ethyl alcohol-water system disappears by A. increasing temperature B. decreasing pressure C. increasing pressure D. no means
12.31 With increase in the concentration of the adsorbate, the integral heat of adsorption A. increases. B. decreases. C. remains unchanged. D. increase or decrease;
13.23 During constant rate drying period, vaporisation rate per unit drying surface area A. decreases with time. B. increases with time. C. does not change with time D. does not affect the moi
13.26 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 B. decreases C. remains unaffected D. passes through a max
13.30 Flooding in a distillation column is detected by sharp A. increase in Murphree plate efficiency. B. decrease in pressure drop. C. decrease in liquid hold up in the coloumn. D. increase in pressure drop.
13.31 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
13.34 At constant pressure, with increase of temperature, the dew point will A. increase B. decrease C. remain unchanged D. increase/decrease;
13.38 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.
13.39 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.
7.4 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
7.12 The relative volatility of a binary mixture at the azeotropic composition is A. 1 B. > 1 C. 0 D. ∞
7.23 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
7.35 At what percentage (by volume) of alcohol composition, it forms an azeotrope with water? A. 90 B. 91.5 C. 95 D. 99
7.41 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
7.44 The value of L / mG ratio for economical absorption operation ranges from A. 0.5 to 0.8 B. 0.8 to 1. C. 1.25 to 2.0 D. 2.5 to 3.
8.28 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
9.11 The operating cost of a distillation column at minimum reflux ratio is A. minimum B. maximum C. infinite D. zero
9.12 The reflux to a distillation column is 100 moles/hr, when overhead product rate is 50 moles/hr. Reflux ratio is A. 2 B. 0.5 C. 50 D. 150
9.14 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
9.22 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
9.47 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 ( K c ) for the same sytem is A. 100 B. 10 C. 5 D. 1
10.15 The rough value of diffusion co-efficient of water vapor into air at 25°C may be about __________ cm 2 /sec. A. 0.25 B. 2.5 C. 1.25 D. 0.
10.37 Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be A. 1 B. > 1 C. < 1 D. ≤ 1
10.38 Selectivity of the solvent used in solvent extraction should be A. 1 B. > 1 C. < 1 D. 0
10.40 Wet bulb and dry bulb temperatures becomes identical at __________ percent saturation curve. A. 100 B. 50 C. 78 D. none
10.44 The most economical range of absorption factor is A. 0 to 0.5 B. 0 to 3 C. 1.25 to 2 D. 5 to 15
11.1 In a binary system, separation is very efficient, when the relative volatility is A. 1 B. > 1 C. < 1 D. 0.
11.18 When the psychometric ratio is ___ then the adiabatic saturation temperature & wet bulb temperature becomes =. A. 1 B. < 1 C. > 1 D. ∞
11.19 Desirable value of absorption factor in an absorber is A. 1 B. < 1 C. > 1 D. 0.
11.22 What is the degree of freedom of an absorption process in which only one component is transferred between phases? A. 3 B. 2 C. 4
12.3 Schimdt number and Lewis number for pure air at atmospheric conditions are respectively A. < 1 and ≈ 1 B. 1 and 0 C. >1 and ≈ 1 D. 0 & ≈ 1
12.13 Degree of freedom for leaching and solvent extraction process is A. 1 B. 3 C. 0 D. 2
12.29 The value of NA /( NA + NB ), for steady state equimolal counter diffusion of two gases ' A ' and ' B ' is A. 1 B. ∞ C. 0.5 D. 2
12.33 If mass diffusivity in a mixture is equal to the thermal diffusivity, then the Lewis number is A. 0 B. 1 C. < 1 D. > 1
12.38 At what value of reflux ratio, number of theoretical plates in a distillation column is minimum? A. 0 B. 1 C. ∞ D. < 1
12.40 In moderate sized packed absorption twr, channeling (most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter A. > 4 :1 B. < 8 : 1 C. > 8:1 D. < 6:
NOT NONE OF THESE
1.4 The term "cooling range" in a cooling tower refers to the difference in the temperature of A. cold water leaving the tower and the wet bulb temperature of the surrounding air. B. hot water entering the tower and the wet bulb temperature of the surrounding air. C. hot water entering the tower and the cooled water leaving the tower. D. none of these
1.10 When the temperature and humidity of air is low, we usually use __________ draft cooling tower. A. natural B. forced C. induced D. none of these
1.21 Relative humidity is the ratio of the A. partial pressure of the vapour to the vapour pressure of the liquid at room temperature. B. partial pressure of the vapour to the vapour pressure of the liquid at gas temperature. C. actual humidity to saturation humidity. D. none of these
1.23 Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the __________ of a fibre. A. electrical resistance B. thermal conductivity C. strength D. none of these.
1.37 Which of the following quantities need not be fixed before starting the design of a co-current absorber? A. Heat gain or loss B. Flow rate of entering liquid C. Flow rate of gas D. None of these
1.38 Mass transfer co-efficient of liquid is A. affected more by temperature than that for gases. B. affected much less by temperature than that for gases. C. not affected by the temperature. D. none of these.
1.42 The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is A. natural draft cooling tower B. induced draft cooling C. spray chamber D. none of these
2.8 The operation involved when the soluble material is largely on the surface of an insoluble solid and is merely washed off by the solvent is called A. decoction B. percolation C. elutriation or elution D. none of these
2.9 In the constant rate period of the rate of drying curve for batch drying, A. cracks develop on the surface of the solid. B. rate of drying decreases abruptly. C. surface evaporation of unbound moisture occurs. D. none of these.
2.21 In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of A. area between operating line and 45° diagonal x-y diagram. B. condenser and reboiler surfaces. C. tower cross-section. D. none of these.
2.22 Wetted wall tower experiment determines the A. molal diffusivity. B. volumetric co-efficient. C. mass transfer co-efficient. D. none of these.
2.25 Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the A. packing may be crushed due to thermal expansion/contraction of the components of the equipments. B. pressure drop in the equipment will be. very high. C. viscosity variation of the fluids may cause channeling/flooding. D. none of these.
2.30 In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction, A. inversely B. linearly C. exponentially D. none of these
2.50 In most of the vacuum crystalliser, vacuum is generally produced by means of a A. suction pump B. compressed air jet C. steam jet ejector with a barometric condenser D. none of these
3.6 A minimum boiling azeotrope is exemplified by A. toluene-benzene B. acetone-carbon disulphide C. water-isobutyl alcohol D. none of these
3.11 As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches A. that of normal condensation. B. integral heat of adsorption. C. zero. D. None of these.
3.17 Only small amount of evaporation of water produces large cooling effects because of its A. large latent heat B. low viscosity C. small latent heat D. none of these
3.22 Flights in a rotary dryer are provided to A. lift and shower the solids thus exposing it thoroughly to the drying action of the gas. B. reduce the residence time of solid. C. increase the residence time of the solid. D. none of these.
