chemical engineering mass transfer Mcqs
201. Pick out the wrong statement ?
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A. erally

B. The equilibrium moisture content of the solid can be reduced by increasing the absolute

C. idity</strong>

D. Elution means the desorption of the adsorbed solute by a solvent

E. Change in barometric pressure does not affect the relative humidity

F. In case of a packed tower, the operating velocity is about half of the flooding velocity,

202. Which of the following is not fixed by the process requirements, in the design of absorbers ?
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A. Flow rate of the entering gas

B. Composition of the entering liquid

C. Terminal concentrations of gas stream

D. None of these
203. In steam distillation, the _____________________?
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A. Temperature is 100C

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

204. Experimental determination of _______________ is done by wetted wall column method?
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A. Mass transfer co-efficient

B. None of these

C. NTU

D. Diffusion co-efficient

205. Danckwerts developed the ____________________ theory?
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A. Surface renewal

B. None of these

C. Penetration

D. Film

206. When an unsaturated air-water mixture is heated at constant pressure, then ____________________ ?
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A. The partial pressure of water vapour increases

B. The relative humidity decreases

C. The specific humidity decreases

D. The relative humidity increases

207. The critical moisture content in case of drying indicates the _______________ rate period?
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A. Beginning of constant

B. None of these

C. Beginning of falling

D. End of falling

208. Which of the following is not a batch drier ?
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A. Agitated pan drier

B. Vacuum shelf drier

C. Fluidised bed drier

D. Truck drier

209. Which of the following is used for the concentration of rubber latex ?
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A. Agitated film evaporator

B. Short tube evaporator

C. Long tube vertical evaporator

D. Calandria

210. With increase in temperature, the mutual solubility of two liquids_________________?
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A. Decreases

B. Increases

C. Decreases exponentially

D. Remains unchanged

211. When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system ?
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A. As the acetone concentration increases, the solubility curves approach each other

B. Both the phases become identical at a particular common point on both the solubility curves

C. led the plait point

D. The distribution curve which is a plot between x (acetone concentration in one phase) and y

E. etone concentration in other phase) is analogous to x-y curve used in distillation and

F. orption terminates on the x = y diagonal at the concentration of the plait point

212. The expression, y(1 x)/x(1 y) is for_____________________?
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A. Relative volatility

B. Murphree efficiency

C. Absorption factor

D. Selectivity

213. 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_________________?
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A. Integral heat of adsorption

B. None of these

C. Differential heat of adsorption

D. Heat of wetting

214. All moisture in a non-hygroscopic material is the ________________ moisture?
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A. Unbound

B. Equilibrium

C. Bound

D. Free

215. 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))_____________?
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A. M(Xo/XF)

B. M ln(Xo/XF)

C. M(Xo XF)

D. MXo ln(Xo/XF)
216. Mass transfer co-efficient is directly proportional to DAB according to the __________ theory?
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A. None of these

B. Penetration

C. Surface-renewal

D. Film
217. Sodium bicarbonate is produced during soda ash manufacture using a _______________ tower?
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A. Baffle

B. Packed

C. None of these

D. Plate

218. The dew point of an unsaturated gas-vapor mixture does not depend upon the _________________ of the mixture?
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A. Total pressure

B. All A, B. and C.

C. Composition

D. Temperature
219. Powdery materials can be guarded against caking tendency on storage by_________________?
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A. Providing minimum percentage of voids

B. Providing irregular grain size

C. None of these

D. Having maximum possible points of contact

220. At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is ________________ percent.?
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A. Between 0 and 100

B. 0

C. 50

D. 100

221. Desulphurisation of petrol is done in a _____________________?
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A. Bollman extractor

B. Plate type extraction column

C. Rotating disc extractor

D. Packed extraction column

222. Molecular diffusivity of a liquid__________________?
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A. Is independent of temperature

B. Decreases with temperature

C. Increases with temperature

D. May increase or decrease with temperature

223. 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 ___________________?
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A. 1

B. 2

C. 0

D. 3

224. 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 hysteresis. In such cases, the desorption equilibrium pressure is ______________ that obtained for adsorption?
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A. Lower than

B. Same as

C. Higher than

D. Either same or higher than

225. At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes______________________?
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A. 1

B. None of these

C. 0

D. ?
226. Water entrained by circulating air in cooling towers is termed as____________________?
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A. Drift

B. None of these

C. Blow down

D. Vapor load

227. For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause ______________ plate requirement?
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A. None of these

B. No change in theoretical

C. Major decrease in the number of

D. Marginal decrease in the number of
228. With the lowering of equilibrium pressure, at a given temperature, the amount of adsorbate on the adsorbent ?
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A. Remain same

B. Decreases

C. Increases

D. Either A. or B., depends on the system

229. The critical moisture content in case of drying indicates the ________________ rate period?
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A. Beginning of falling

B. None of these

C. End of falling

D. Beginning of constant

230. Pick out the wrong statement. Generally for physical adsorption, a gas of________________?
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A. Higher molecular weight is adsorbed in preference to a gas of low molecular weight

B. Low volatility is adsorbed in preference to a gas of high volatility

C. None of these

D. High critical temperature is adsorbed in preference to a gas of low critical temperature

231. Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the____________________?
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A. Pressure drop in the equipment will be very high

B. None of these

C. ipments</strong>

D. Packing may be crushed due to thermal expansion/contraction of the components of the

E. Viscosity variation of the fluids may cause channelling/flooding

232. Can the efficiency of a plate in the distillation tower be greater than 100% ?
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A. Never

B. Normally not; but is possible if infinite number of plates are put

C. Yes

D. Yes; if the reflux ratio is maximum

233. In liquid extraction, if the selectivity is unity, then___________________?
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A. Separation of the constituents is the most effective

B. Solvent flow rate should be very low

C. Amount of solvent required will be minimum

D. No separation will occur
234. Steam distillation is used to__________________?
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A. Increase the total pressure of distillation

B. Increase the efficiency of separation

C. Reduce the number of plates

D. Avoid thermal decomposition of a component
235. 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) ?
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A. T

B. ?T

C. T3

D. T2
236. Pick out the wrong statement pertaining to the cooling towers ?
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A. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb

B. peratur</strong>e

C. A natural draft cooling tower is recommended to be used, when the air humidity is low and air

D. In case of induced draft cooling tower, the fan is placed at the top of the tower

E. perature is also low

F. discharged air

237. For a ternary mixture, in which equilateral triangular co-ordinate is used in leaching and extraction, a ____________ of the equilateral triangular co-ordinates?
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A. Ternary mixture is represented by the sides

B. Binary mixture is represented by any point inside

C. Binary mixture is represented by the apex

D. Pure component is represented by the apex
238. The equation, NA = (DAB . Pt /RTZ) (y1 y2) is for _______________________?
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A. Liquid M.T.C. by penetration theory

B. Ficks first law of diffusion

C. Steady state diffusion for stagnant case

D. Steady state equimolar counter diffusion
239. Weeping in a distillation column_____________________?
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A. Increases tray efficiency

B. Results due to very high gas velocity

C. Provides large interfacial surface for mass transfer

D. Results due to very low gas velocity
240. Rayleighs equation applies to ________________ distillation?
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A. Continuous

B. Steam

C. Differential

D. Flash

241. 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)_________________?
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A. 900

B. 1200

C. 800

D. 500
242. Pick out the wrong statement ?
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A. In case of a stripper, the equilibrium curve is always below the operating line

B. Absorption factor is constant, when the equilibrium and operating lines are straight

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

243. According to Poiseuilles law, the permeability for gas flow through a capillary is proportional to (where, ? = gas viscosity)___________________?
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A. 1/?

B. ??

C. ?2

D. ?

244. Moisture in a solid exerting an equilibrium vapour pressure equal to that of the pure liquid at the same temperature is called the ___________________ moisture ?
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A. Critical

B. Free

C. Unbound

D. Bound

245. 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

246. Which of the following can be calculated theoretically using steam table and Daltons law of partial pressure; if the relative humidity and dry bulb temperature of moist air is known ?
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A. Humidity ratio

B. None of these

C. Wet bulb temperature

D. Dew point

247. Alcohol is dehydrated using _______________________ distillation?
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A. Extractive

B. Azeotropic

C. Molecular

D. Steam

248. Pick out the wrong statement ?
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A. nomy

B. With increase in pressure, the solubility of gases in solvent increases at a fixed temperature

C. In solvent extraction, the distribution co-efficient should be as large as possible for solvent

D. The capacity of a distillation column is maximum at total reflux

E. Decrease in Murphree plate efficiency is an indication of entrainment in distillation column

249. The slope of the operating line for a single component co-current absorber when plotted in terms of mole ratio units is__________________?
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A. -ve

B. #NAME?

C. ?

D. 0

250. Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the_________________?
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A. High evaporation losses of water

B. Difficulty in its fabrication

C. High pressure drop of the gas

D. None of these