chemical engineering mass transfer Mcqs
151. For the flow of gases through a capillary, with increase in temperature, the permeability __________________ as per Knudsen law?
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A. Increases

B. Either A. or B.; depends on the gas

C. Decreases

D. Remain same

152. Which of the following has the same dimension as mass diffusivity ?
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A. Momentum flux

B. Kinematic viscosity

C. Thermal diffusivity

D. Both B. and C.
153. Large quantity of silica gel is normally dried in a _________________ dryer?
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A. Rotary vacuum

B. Freeze

C. Tray

D. Through circulation
154. Ammonia present in the coke oven gas is removed by washing with___________________?
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A. Caustic solution

B. Dilute ammoniacal liquor

C. Dilute HCl

D. Ethanolamine

155. The individual mass transfer co-efficients (moles/m2s) 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 ?
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A. Liquid side

B. Gas side

C. Interfacial

D. Both liquid and gas side

156. For a single component absorber, the operating line is straight only when plotted in term of ______________ units?
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A. Mole ratio

B. Partial pressure

C. Mole fraction

D. None of these

157. Which of the following is directly concerned with Psychrometry ?
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A. Galileo number

B. Lewis relationship

C. Dean number

D. Weber number

158. Steady state equimolal counter diffusion is encountered in_____________________?
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A. Absorption of NH3 from air by water

B. All liquid-solid diffusion systems

C. Separation of a binary mixture by distillation

D. All liquid-liquid diffusion systems

159. Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant______________________?
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A. Humidity

B. All A., B. & C.

C. Velocity

D. Temperature

160. The cooling effect in a cooling tower cannot be increased by_____________________?
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A. Lowering the barometric pressure

B. Reducing the humidity of entering air

C. None of these

D. Increasing the air velocity over the wet surfaces

161. In extraction, as the temperature increases, the area of heterogeneity (area covered by binodal curve)________________?
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A. Decreases

B. None of these

C. Increases

D. Remains unchanged

162. Most important factor to be considered in the selection of packings for absorbers is the ______________ of packing?
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A. Cost

B. Porosity

C. Durability

D. Size

163. With increase in temperature, the mutual solubility of two liquids___________________?
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A. Remains unchanged

B. Increases

C. Decreases exponentially

D. Decreases

164. Packed column distillation is limited to the column _____________ metres?
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A. Height < 6

B. Diameter < 0.6

C. Both A. & B.

D. Neither A. nor B.

165. A slurry is to be dried to produce flaky solid. Which dryer would you recommend ?
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A. Rotary dryer

B. Drum dryer

C. Dielectric dryer

D. Spray dryer
166. _____________ extractor is used for the concentration of radioactive nuclear waste?
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A. Sieve plate

B. Bollman

C. Mixer-settler

D. Pulsed column
167. Diameter of raschig rings used in packed tower in industry is normally around _____________________ inches?
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A. 12

B. 18

C. 8

D. 2
168. In case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of _______________ is zero?
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A. Gas phase

B. All A , B. & C.

C. Liquid phase

D. Interface
169. Raschig ring made of porcelain cannot be used for treating concentrated___________________?
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A. Hydrochloric acid

B. Nitric acid

C. Sulphuric acid

D. Alkalis
170. Paper industry employs _____________ driers ?
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A. Rotary

B. Cylinder

C. Fluidised bed

D. Spray

171. Pressure drop through plate tower as compared to that through packed tower, for the same duty will be___________________?
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A. Either A. or B.; depends on the packing height

B. Less

C. Equal

D. More
172. At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes_____________________?
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A. 1

B. 0

C. ?

D. None of these

173. Lewis number (Le) is____________________?
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A. Sc Pr

B. Sh Pr

C. Pr St

D. St Sh

174. Reboiler is considered as one theoretical plate, because_____________________?
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A. Reboiler itself contains one plate

B. None of these

C. Vapour is recycled to the column

D. Of the assumption that vapour and liquid leaving the reboiler are in equilibrium
175. The wet and dry bulb temperature for a vapour-gas mixture are 25C and 30C respectively. If the mixture is heated to 45C at constant pressure, the wet bulb temperature will be ______________ C?
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A. > 25

B. 25

C. 25

D. < 25

176. With increase in temperature, the rate of leaching increases, because the___________________?
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A. Diffusivity of solute increases

B. Thermal conductivity of solute increases

C. Viscosity of solvent decreases

D. None of these

177. Design calculation for multiple component distillation is done by_________________?
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A. Tray to tray calculations

B. Enthalpy concentration method

C. Ponchon-Savarit method

D. McCabe-Thiele method

178. Large scale usage of flash distillation is practised in __________________?
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A. Polymerisation industry

B. Ammonia synthesis plant

C. Soap manufacturing

D. Petroleum refining
179. 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___________________?
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A. 2 metres above the ground

B. At ground level

C. 5 metres above ground

D. 10 metres above ground

180. Reverse osmosis is also called_________________?
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A. Dialysis

B. Ultra-filtration

C. Diffusion

D. Electrodialysis

181. Leaching rate is independent of the________________?
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A. None of these

B. Particle size

C. Temperature

D. Agitation

182. Which is not concerned directly with mass transfer ?
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A. Schmidt number

B. Lewis relationship

C. Sherwood number

D. Froude number
183. Powdery materials can be guarded against caking tendency on storage by___________________?
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A. Providing minimum percentage of voids

B. Having maximum possible points of contact

C. None of these

D. Providing irregular grain size

184. Experimental determination of ________________ is done by wetted wall column method?
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A. Diffusion co-efficient

B. Mass transfer co-efficient

C. NTU

D. None of these

185. 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_______________________?
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A. 5

B. 100

C. 1

D. 10
186. When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is _______________ distillation?
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A. Continuous

B. Azeotropic

C. None of these

D. Steam
187. The diffusivity D. in a binary gas mixture is related to the pressure (P) as__________________?
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A. D ? 1/P1.5

B. D ? 1/P

C. D ? P0.5

D. D ? 1/P0.5

188. Steady state temperature reached by a small amount of liquid evaporating into a large amount of unsaturated vapour-gas mixture is called the ________________ temperature?
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A. Dew point

B. Wet-bulb

C. Dry-bulb

D. Adiabatic saturation

189. _______________ extractor is used for the concentration of radioactive nuclear waste?
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A. Sieve plate

B. Pulsed column

C. Mixer-settler

D. Bollman

190. Large scale drying of wheat is done in a ________________ dryer?
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A. Fluidised bed

B. Spouted bed

C. Tray

D. Vacuum rotary

191. Tower diameter may be decreased by__________________?
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A. Increasing the vapour flow rate

B. Increasing the liquid flow rate

C. Using higher reflux ratio

D. Use of increased tray spacing
192. Water entrained by circulating air in cooling towers is termed as________________?
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A. Blow down

B. Vapor load

C. Drift

D. None of these

193. Leaching of coarse solid lumps is also termed as _____________________?
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A. Dissolution

B. Percolation

C. Agitation and settling

D. Decoction

194. Mass transfer co-efficient is defined as__________________?
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A. Co-efficient = Flux/concentration difference

B. None of these

C. Flux = Co-efficient/concentration difference

D. Flux=concentration difference/coefficient

195. 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 raffinate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg) ?
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A. 6.89

B. 8.89

C. 8.25

D. 10

196. Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of _______________ humidity?
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A. Percentage

B. Molal

C. Relative

D. None of these

197. The main reason for dividing a tall packed tower into series of small towers is to________________________?
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A. Minimise the overall pressure drop

B. Avoid channelling

C. Avoid flooding

D. Reduce liquid hold up

198. The value of NA/(NA + NB) for steady state molecular diffusion of gas A through nondiffusing gas B is____________________?
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A. 2

B. ?

C. 1

D. 0.5

199. Acetic acid will be most economically separated from a dilute solution of acetic acid in water by____________________?
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A. Solvent extraction

B. Evaporation

C. Continuous distillation

D. Absorption

200. Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of _______________ humidity?
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A. Molal

B. Percentage

C. None of these

D. Relative