chemical engineering mass transfer Mcqs
401. The value of NA/(NA + NB), for steady state equimolal counter diffusion of two gases A and B is____________?
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A. ?

B. 1

C. 2

D. 0.5

402. The relative humidity of air decreases in-spite of an increase in the absolute humidity, when the____________________?
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A. Pressure rises

B. Temperature rises

C. Pressure falls

D. Temperature falls

403. According to Chilton-Colburn analogy for mass transfer, NSt.NSc 2/3 is equal to_________________?
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A. f/2

B. 2f

C. f

D. 1/f

404. Very tall packed towers are divided into series of beds to___________________?
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A. Reduce liquid hold-up

B. Reduce the overall pressure drop

C. Avoid channelling

D. Avoid flooding

405. A liquid mixture contains 30% o-xylene, 60% p-xylene and 10%. m-xylene (all percentages in w/w). Which of the following statements would be true in respect of this mixture ?
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A. The mixture contain optical isomers

B. The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10

C. The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and mxylene

E. The mixture exhibits an azeotrope at 101.3 kPa
406. In stripping section of continuous distillation column, the_______________________?
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A. Liquid is enriched with high boiler

B. None of these

C. Vapour is stripped of low boiler

D. Liquid is stripped of high boiler

407. A minimum boiling azeotrope is exemplified by__________________________?
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A. Toluene-benzene

B. Water-isobutyl alcohol

C. None of these

D. Acetone-carbon disulphide
408. Binary distillation involves the mass transfer by ______________________ at the gas-liquid interface?
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A. Either A. or B.

B. Unidirectional diffusion from gas to liquid phase

C. A counter diffusion at an almost equal molar rate

D. Unidirectional diffusion from liquid to gas phase

409. In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at ________________ reflux ?
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A. Maximum permissible

B. Total

C. Operating

D. Minimum

410. As per Gillilands equation, the diffusivity is___________________?
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A. Inversely proportional to P

B. Dependent on the molecular volume & molecular weight of components

C. Directly proportional to T1.5

D. All A , B. & C.
411. 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________________?
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A. Ideal gases

B. Non-Newtonian liquids

C. Newtonian liquids

D. Real gases

412. A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process ?
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A. Humidity of inlet air

B. Temperature of the solid

C. Flow rate of inlet air

D. Relative humidity of outlet air

413. The Schmidt number which is defined as, ?/? D, is the ratio of the_____________________?
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A. Momentum diffusivity to the mass diffusivity

B. Momentum diffusivity to the thermal diffusivity

C. Thermal diffusivity to the mass diffusivity

D. None of these

414. Absorption factor, for a fixed degree of absorption from a fixed amount of gas should be_________________?
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A. < 1

B. > 1

C. ? 1

D. 1

415. The percentage humidity is less than the relative humidity only at __________________ percent humidity?
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A. Zero

B. Hundred

C. Both zero and hundred

D. None of these

416. Below is given an equilibrium moisture curve of a substance. State which regions represent free moisture and unbound moisture respectively ?
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A. IV, II

B. II, III

C. II, IV

D. IV, III

417. Detergent solution is dried to a powder in a ________________________?
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A. Spray dryer

B. Spouted bed dryer

C. Tunnel dryer

D. Pan open to atmosphere

418. Sand is dried in foundries in a ______________________drier?
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A. Spray

B. Fluidised bed

C. Vacuum

D. Rotary

419. Which of the following binary systems is an example of a maximum boiling azeotrope ?
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A. Water-hydrochloric acid

B. Water-ethyl alcohol

C. n-heptane-n-octane

D. Acetone-carbon disulphide

420. Smoke is an example of ___________________?
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A. Liquid dispersed in gas

B. Solid dispersed in liquid

C. Gas dispersed in liquid

D. Solid dispersed in gas
421. A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state ?
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A. Composition of vapors and that of liquid do not vary throughout the column

B. The top and bottom compositions correspond to the maximum enrichment available

C. The top and bottom compositions are unchanged with and without total reflux

D. Reboiler load and condenser load are minimum

422. Azeotropism for ethyl alcohol-water system disappears by_____________________?
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A. Decreasing pressure

B. Increasing pressure

C. No means

D. Increasing temperature

423. Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the ________________ of a fibre ?
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A. None of these

B. Thermal conductivity

C. Electrical resistance

D. Strength

424. For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will_____________________?
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A. Data insufficient, cant be predicted

B. Remain same

C. Decrease

D. Increase
425. Schmidt number and Lewis number for pure air at atmospheric conditions are respectively__________________?
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A. > 1 and ? 1

B. < 1 and ? 1

C. 0 and ? 1

D. 1 and 0

426. Component A is diffusing in a medium B. The flux NA relative to a stationary point is equal to the flux due to molecular diffusion, if____________________?
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A. There is equimolar counter diffusion

B. Mass transfer is accompanied by reaction

C. Diffusion of A is in stagnant medium B

D. Molecular mean free path is high

427. The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is___________________?
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A. +ve

B. None of these

C. Zero

D. #NAME?

428. With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas________________?
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A. Increases

B. Decreases linearly

C. Remain unaffected

D. Decreases
429. In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of_______________________?
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A. None of these

B. Condenser and reboiler surfaces

C. Area between operating line and 45 diagonal x-y diagram

D. Tower cross-section

430. In case of an unsaturated mixture of gas and vapor, the percentage saturation is __________________ its relative saturation?
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A. Higher than

B. Either A. or B., depends on the mixture composition

C. Equal to

D. Lower than
431. Calcium ammonium nitrate (a fertiliser) is dried in a _________________ dryer?
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A. Tunnel

B. Vacuum

C. Tray

D. Rotary
432. Mass transfer co-efficient (K) and diffusivity D. are related according to film theory as______________________?
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A. K ??D

B. K ? D

C. K ? D1.5

D. K ? D2

433. Moisture contained by a substance in excess of the equilibrium moisture is called the _______________ moisture?
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A. Free

B. Bound

C. Unbound

D. Critical

434. For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around____________________?
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A. 1

B. 0.6

C. 0.24

D. 0.72

435. With increase in temperature, the solubility of gases in liquids, at fixed pressure____________________?
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A. Remain same

B. Decreases

C. Increases

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

436. The term approach in a cooling tower refers to the difference in the temperature of the____________________?
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A. Hot water entering and the cooled water leaving the cooling tower

B. Cold water leaving the tower and the wet bulb temperature of the surrounding air

C. Hot water entering the tower and the wet bulb temperature of the surrounding air

D. None of these

437. Molecular sieves are porous____________________?
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A. Silica

B. Alumina

C. None of these

D. Synthetic zeolites crystals/metal alumino-silicates
438. Rose oil is extracted from rose leaves using ____________ distillation?
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A. Steam

B. High pressure

C. Low pressure

D. Extractive

439. Acetone is to be removed from air in an isothermal dilute absorber using pure water as solvent. The incoming air contains 5 mole% of acetone (yin = 0.05). The design equation to be used for obtaining the number of trays (N) of the absorber is, N+2 = 6 log (yin/yout).For 98% recovery of acetone, the number of trays required is/are ?
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A. 4

B. 8

C. 9

D. 10

440. Small dia distillation column can be a _________________________?
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A. Bubble cap

B. Any of these

C. Sieve tray

D. Packed column
441. 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?
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A. Same as

B. Less than

C. Very much less

D. More than
442. The solvent used in liquid-liquid extraction should have _______________ less than one?
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A. Selectivity

B. Distribution co-efficient

C. Both A. and B.

D. Neither A. nor B.
443. Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve) ____________________?
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A. S1 S2

B. S2/S1

C. S1/S2

D. S1 S2

444. An alkaline solution is used to reduce the concentration of carbon dioxide in a stream from 10% to 0.1% by absorption with irreversible chemical reaction. The overall number of transfer units based on gas phase is ?
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A. 100

B. 4.605

C. 9.21

D. 0.001

445. Which of the following is an undesirable characteristic for the solvent used in gas absorption ?
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A. Low viscosity

B. High gas solubility

C. None of these

D. Low vapor pressure

446. Which of the following adsorbent is used to decolourise yellow glycerine ?
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A. Fullers earth

B. Alumina

C. Silica gel

D. Activated carbon
447. Flash distillation is suitable for separating the constituents of a binary system, which _____________________?
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A. Have very close boiling points

B. Have very wide boiling points

C. Form constant boiling azeotrope

D. Form minimum boiling azeotrope

448. _______________ diffusion is used for separating the isotopes of methane ?
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A. Thermal

B. Concentration

C. Force

D. Pressure

449. In a distillation operation, what is the effect of the temperature of the reflux stream (given below) on the condenser and reboiler loads? Reflux conditions: (i) Reflux stream is completely liquid and is at its bubble point. (ii) Reflux stream is below its bubble point ?
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A. Condenser and reboiler loads are the same in both the cases

B. Reboiler load is the same in both the cases but condenser load is higher in case (ii)

C. Condenser load is the same in both the cases but reboiler load is higher in case (ii)

D. Both condenser and reboiler loads are higher in case (ii) as compared to case (i)
450. In McCabe-Thiele method, at infinite reflux ratio________________?
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A. The overhead product is minimum

B. Both the operating lines coincide with diagonal

C. Both A. and B.

D. Neither A. nor B.