Mass Transfer Mcqs for Chemical - Set 1

1)   According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (αAB = 2) does not change appreciably in the column ?

a. 5
b. 9
c. 12
d. 28
Answer  Explanation 

ANSWER: 12

Explanation:
No explanation is available for this question!


2)   During the constant rate period of drying of a solid ?

a. Increased air humidity decreases the rate of drying
b. Increasing the air temperature decreases the drying rate
c. Surface evaporation of unbound moisture occurs
d. None of these
Answer  Explanation 

ANSWER: Surface evaporation of unbound moisture occurs

Explanation:
No explanation is available for this question!


3)   Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is___________________?

a. Insoluble in the liquid
b. Soluble in the liquid
c. Non-ideal in nature
d. At a fixed temperature
Answer  Explanation 

ANSWER: Insoluble in the liquid

Explanation:
No explanation is available for this question!


4)   As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages_______________________?

a. Increase
b. Decrease
c. Remain unchanged
d. Can either increase or decrease, depends on the system
Answer  Explanation 

ANSWER: Decrease

Explanation:
No explanation is available for this question!


5)   Large scale drying of sugar is done in a _______________ dryer?

a. Spouted bed
b. Tray
c. Rotary
d. Truck
Answer  Explanation 

ANSWER: Rotary

Explanation:
No explanation is available for this question!


6)   H2S is being absorbed in a gas absorber unit. The height of the transfer unit based on the overall mass transfer coefficient on the gas side is 0.4 m. The equilibrium data is given by, y = 1.5 x. The bulk concentration of H2S has to be reduced from 0.05 to 0.001 mole fraction in the gas side. The height of the tower (in meters) corresponding to an operating line given by, y = 5x + 0.001 is ______________________?

a. 2.0
b. 1.56
c. 1.0
d. 0.56
Answer  Explanation 

ANSWER: 2.0

Explanation:
No explanation is available for this question!


7)   Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 × 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is _________________________?

a. 5.6 × 10-4
b. 8.5 × 10-4
c. 5.6 × 10-3
d. 8.5 × 10-3
Answer  Explanation 

ANSWER: 8.5 × 10-4

Explanation:
No explanation is available for this question!


8)   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
Answer  Explanation 

ANSWER: Pure gas

Explanation:
No explanation is available for this question!


9)   _______________ equation applies to diffusivities in liquids?

a. Gilliland
b. Hirschfelder
c. Wilke and Chang
d. None of these
Answer  Explanation 

ANSWER: Gilliland

Explanation:
No explanation is available for this question!


10)   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
Answer  Explanation 

ANSWER: Decreases with increase in

Explanation:
No explanation is available for this question!


11)   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
d. Dependent on the Reynolds number
Answer  Explanation 

ANSWER: Dependent on the Reynolds number

Explanation:
No explanation is available for this question!


12)   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
Answer  Explanation 

ANSWER: log P vs. T

Explanation:
No explanation is available for this question!


13)   The commonly used solvent in supercritical extraction is_____________________?

a. Methyl ethyl ketone
b. Water
c. Carbon tetrachloride
d. Carbon dioxide
Answer  Explanation 

ANSWER: Carbon dioxide

Explanation:
No explanation is available for this question!


14)   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; depends on the type of liquid
Answer  Explanation 

ANSWER: Increase

Explanation:
No explanation is available for this question!


15)   The equation, NA = (DAB . Pt /RTZ . PBM) (PA1 – PA2) is for_______________________?

a. Fick’s second law of diffusion
b. Steady state diffusion for stagnant case
c. Liquid M.T.C. by Higbie penetration theory
d. None of these
Answer  Explanation 

ANSWER: Steady state diffusion for stagnant case

Explanation:
No explanation is available for this question!


16)   Perforated plate towers are unique for solvent extraction because, they provide_____________________?

a. Higher contact area
b. Better contact of the phase
c. Repeated coalescence & redispersion of the drop phase
d. None of these
Answer  Explanation 

ANSWER: Repeated coalescence & redispersion of the drop phase

Explanation:
No explanation is available for this question!


17)   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, moles/m2, a: interfacial area per unit volume of tower) ?

a. G/(FG . a)
b. FG/(G . a)
c. (G . a)/FG
d. L/(FG . G)
Answer  Explanation 

ANSWER: G/(FG . a)

Explanation:
No explanation is available for this question!


18)   Pore size of the molecular sieve 5A is ____________________ mm ?

a. 5
b. 0.5
c. 0.05
d. 50
Answer  Explanation 

ANSWER: 0.5

Explanation:
No explanation is available for this question!


19)   To remove all the moisture from a wet solid it requires exposure to _____________ air?

a. Perfectly dry
b. Highly humid
c. High temperature
d. None of these
Answer  Explanation 

ANSWER: Perfectly dry

Explanation:
No explanation is available for this question!


20)   The cooling effect in a cooling tower can be speeded up by _______________________?

a. Increasing the air velocity and area of exposed wet surface
b. Reducing the barometric pressure
c. Reducing the humidity of the air
d. All A., B. and C.
Answer  Explanation 

ANSWER: All A., B. and C.

Explanation:
No explanation is available for this question!


21)   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 glycerine
Answer  Explanation 

ANSWER: Decolouration of yellow glycerine

Explanation:
No explanation is available for this question!


22)   The Knudsen diffusivity is proportional to (where, T = absolute temperature) ______________________?

a. √T
b. T2
c. T
d. T4
Answer  Explanation 

ANSWER: √T

Explanation:
No explanation is available for this question!


23)   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. 90-10
Answer  Explanation 

ANSWER: 10-15

Explanation:
No explanation is available for this question!


24)   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. Decreases exponentially
Answer  Explanation 

ANSWER: Increases

Explanation:
No explanation is available for this question!


25)   For the flow of gases through a capillary, with increase in temperature, the permeability __________________ as per Knudsen law?

a. Increases
b. Decreases
c. Remain same
d. Either A. or B.; depends on the gas
Answer  Explanation 

ANSWER: Increases

Explanation:
No explanation is available for this question!


26)   Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the _______________ moisture?

a. Free
b. Unbound
c. Equilibrium
d. Bound
Answer  Explanation 

ANSWER: Equilibrium

Explanation:
No explanation is available for this question!


27)   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
Answer  Explanation 

ANSWER: Liquid side coefficient should be increased

Explanation:
No explanation is available for this question!


28)   The relative volatility of a binary mixture at the Azeotropic composition is _______________________?

a. 1
b. > 1
c. 0
d.
Answer  Explanation 

ANSWER: 1

Explanation:
No explanation is available for this question!


29)   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. (4De/πt)1/2
d. (4De/t)
Answer  Explanation 

ANSWER: (4De/πt)1/2

Explanation:
No explanation is available for this question!


30)   The equation, NA = (DAB . Pt /RTZ) (y1 – y2) is for _______________________?

a. Steady state equimolar counter diffusion
b. Fick’s first law of diffusion
c. Steady state diffusion for stagnant case
d. Liquid M.T.C. by penetration theory
Answer  Explanation 

ANSWER: Steady state equimolar counter diffusion

Explanation:
No explanation is available for this question!


31)   Coffee is prepared from coffee beans by leaching with____________________?

a. Cold water
b. Hot water
c. Dilute hot caustic solution
d. Naphtha
Answer  Explanation 

ANSWER: Hot water

Explanation:
No explanation is available for this question!


32)   Which of the following parameters remains constant during chemical dehumidification ?

a. Dry bulb temperature
b. Partial pressure of vapour
c. Wet bulb temperature
d. None of these
Answer  Explanation 

ANSWER: Dry bulb temperature

Explanation:
No explanation is available for this question!


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

a. Spray dryer
b. Drum dryer
c. Rotary dryer
d. Dielectric dryer
Answer  Explanation 

ANSWER: Spray dryer

Explanation:
No explanation is available for this question!


34)   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
Answer  Explanation 

ANSWER: Product must be immiscible with water

Explanation:
No explanation is available for this question!


35)   Dried finished product sampled from various parts of a ________________ dryer exhibits nonuniformity in the moisture content?

a. Rotary
b. Tray
c. Freeze
d. None of these
Answer  Explanation 

ANSWER: Tray

Explanation:
No explanation is available for this question!


36)   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) ?

a. 6.89
b. 8.89
c. 10
d. 8.25
Answer  Explanation 

ANSWER: 8.89

Explanation:
No explanation is available for this question!


37)   The value of „L/mG’ ratio for economical absorption operation ranges from _____________________?

a. 0.5 to 0.8
b. 0.8 to 1.2
c. 1.25 to 2.0
d. 2.5 to 3.5
Answer  Explanation 

ANSWER: 1.25 to 2.0

Explanation:
No explanation is available for this question!


38)   Large quantity of silica gel is normally dried in a _________________ dryer?

a. Freeze
b. Through circulation
c. Rotary vacuum
d. Tray
Answer  Explanation 

ANSWER: Through circulation

Explanation:
No explanation is available for this question!


39)   Mass transfer co-efficient is defined as__________________?

a. Flux = Co-efficient/concentration difference
b. Co-efficient = Flux/concentration difference
c. Flux=concentration difference/coefficient
d. None of these
Answer  Explanation 

ANSWER: Co-efficient = Flux/concentration difference

Explanation:
No explanation is available for this question!


40)   Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be__________________?

a. Cooled
b. Humidified
c. Both A. & B.
d. Dehumidified
Answer  Explanation 

ANSWER: Humidified

Explanation:
No explanation is available for this question!