0% 0 Mass Transfer Quiz 7 1 / 50 Leaching of uranium ore and gold ore is done in__________? Centrifugal extractor Bollman extractor None of these Pachuca tanks 2 / 50 Minimum reflux ratio in a distillation column results in___________? Optimum number of trays Maximum condenser size Minimum number of trays Minimum reboiler size 3 / 50 Molecular sieves are porous______? Silica Alumina None of these Synthetic zeolites crystals/metal alumino-silicates 4 / 50 Minimum reflux ratio in a distillation column results in_______? Optimum number of trays Minimum reboiler size Minimum number of trays Maximum condenser size 5 / 50 Molecular diffusion is caused by the_________? Transfer of molecules from low concentration to high concentration region Potential energy of the molecules Activation energy of the molecules Thermal energy of the molecules 6 / 50 Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the _____ moisture ? Free Unbound Critical Bound 7 / 50 Only small amount of evaporation of water produces large cooling effects because of its_____? Low viscosity Large latent heat Small latent heat None of these 8 / 50 Liquid diffusivity is of the order of ________ cm2 /second? 10-5 to 10-6 0.1 > 1 0.01 9 / 50 Leaching of coffee from coffee beans is done by_____? Hexane Dilute H2SO4 (hot) Hot water Lime water 10 / 50 Make up water is supplied during cooling tower operation to compensate for water losses due to________? Blowdown All A., B. & C. Evaporation Entrainment 11 / 50 Nitrobenzene (boiling point = 210.6?C) is steam distilled at 1 atm pressure. Nitrobenzene will distil off ________ ?C? None of these At < 100 At > 210.6 Between 100 and 210 12 / 50 Most important factor to be considered in the selection of packings for absorbers is the _______ of packing? Cost Size Durability Porosity 13 / 50 Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a _________ column? Wetted wall Spray Packed Bubble cap plate 14 / 50 Most important factor to be considered in the selection of packings for absorbers is the _______ of packing? Durability Size Cost Porosity 15 / 50 Operating velocity in a packed tower is usually ___________ the flooding velocity ? More than Twice Half Equal to 16 / 50 Low viscosity absorbent is preferred for reasons of ______? Rapid absorption rates and good heat transfer characteristics Low pressure drop on pumping All A., B. and C. Improved flooding characteristics 17 / 50 McCabe-Thiele method_________? Uses molal units for material and energy balance Uses weight fractions to express liquid and vapour composition Can use any type of units Is more accurate than Ponchon-Savarit method 18 / 50 Lewis number (Le) is______? St ? Sh Sc ? Pr Pr ? St Sh ? Pr 19 / 50 On addition of solute in the solvent, the _______ of the solution decreases ? Vapour pressure Freezing point Both B. and C. Boiling point 20 / 50 Mass transfer rate between two fluid phases does not necessarily depend on the _______ of the two phases? Degree of turbulence Chemical properties Physical properties Interfacial area 21 / 50 Ordinary diffusion process is also called _______ diffusion? Concentration Thermal Forced Pressure 22 / 50 Occurrence of ?case hardening? during drying of a high moisture solid cake ________ the drying rate? Does not affect Increases Exponentially increases Decreases 23 / 50 Mass transfer co-efficient varies as DAB 0.5, according to the ________ theory? Surface renewal Film Penetration None of these 24 / 50 Lewis number, which is important in problems involving simultaneous heat and mass transfer, is the ratio of___________? Thermal diffusivity to mass diffusivity Mass diffusivity to momentum diffusivity Momentum diffusivity to thermal diffusivity None of these 25 / 50 Mass transfer co-efficient is directly proportional to DAB 0.5, according to _________ theory ? Film None of these Surface renewal Penetration 26 / 50 Lewis number (Le) is_____? Pr ? St Sc ? Pr Sh ? Pr St ? Sh 27 / 50 Molecular diffusivity of a liquid___________? Increases with temperature May increase or decrease with temperature Is independent of temperature Decreases with temperature 28 / 50 Mass transfer co-efficient of liquid is______? None of these Affected much less by temperature than that for gases Affected more by temperature than that for gases Not affected by the temperature 29 / 50 Minimum possible diameter of a packed column is decided mainly by the__________? Liquid density Liquid hold up Gas viscosity Flooding 30 / 50 Moisture contained by a substance in excess of the equilibrium moisture is called the ________ moisture? Bound Critical Free Unbound 31 / 50 Make up water is required in a cooling tower to replace the water lost by_____? Evaporation Blowdown and leakage Drift All A., B. and C. 32 / 50 One mole feed of a binary mixture of a given composition is flash vaporised at a fixed P and T. If Raoult?s law is obeyed, then changing the feed composition would effect ? The fraction vaporised but not the product composition The product composition as well as the fraction vaporised Neither the product composition nor the fraction vaporised The product composition but not the fraction vaporised 33 / 50 Mass transfer co-efficient is directly proportional to DAB according to the ______ theory? Surface-renewal None of these Penetration Film 34 / 50 On moving the feed line (q-line) from saturated liquid feed (vertical position) to saturated vapor feed (horizontal feed), if the slope of both the operating lines are to be increased, then it will result in________? None of these Greater degree of separation with a fixed number of trays Increased reflux ratio Increased reboiler load 35 / 50 Milk is dried usually in a ___________ dryer? Spray Tray Rotary Freeze 36 / 50 Leaching of sugar from sugar beets is done by_____? Dilute H2SO4 Hot water Hexane Lime water 37 / 50 Mass transfer co-efficient is directly proportional to DAB according to the __________ theory? Penetration None of these Surface-renewal Film 38 / 50 Mechanism of moisture removal in case of freeze drying of food stuff is by _____? Adsorption Sublimation Dehydration Evaporation 39 / 50 Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a ________ column? Spray Packed Wetted wall Bubble cap plate 40 / 50 Molality is defined as the number of gm moles of solute per __________ of solvent ? m3 Litre Kg gm 41 / 50 Mass transfer co-efficient ?K? according to penetration theory varies with mass diffusivity as______? D0.5 D1.5 1/D D 42 / 50 McCabe-Thiele method of binary distillation does not assume that the___________? Sensible heat changes are negligible compared with latent heat changes Heat of mixing is negligible None of these Molar latent heats of all components are equal 43 / 50 Leaching of uranium ore and gold ore is done in_______? None of these Centrifugal extractor Bollman extractor Pachuca tanks 44 / 50 Molarity is defined as the number of gm moles of solute per _________ of solvent? c.c Litre kg gm 45 / 50 Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the ________ moisture? Free Equilibrium Bound Unbound 46 / 50 Molecular sieves are regenerated by heating to _______ ?C? > 1000 < 150 > 500 200-330 47 / 50 NSc/NPr is called the________? Stanton number Lewis number Sherwood number Psychrometric ratio 48 / 50 Molecular distillation is_______? Very low pressure distillation High temperature distillation Both B. and C. For heat-sensitive materials 49 / 50 Leaching rate is independent of the_________? Agitation Particle size Temperature None of these 50 / 50 Mass transfer co-efficient (K) and diffusivity D. are related according to film theory as________? K ? D1.5 K ??D K ? D K ? 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