Mass Transfer Mcqs for Chemical - Set 15

1)   Pick out the correct statement ?

a. In case of liquid-liquid extraction, no separation is possible, if the selectivity of the solvent used is unity
b. With increase in temperature, the selectivity of the solvent used in solvent extraction decreases
c. The selectivity of solvent used in solvent extraction is unity at the plait point
d. All A., B. and C.
Answer  Explanation 

ANSWER: All A., B. and C.

Explanation:
No explanation is available for this question!


2)   Pick out the wrong statement?

a. When the concentration difference for the mass transfer becomes zero at the bottom of the gas absorption tower, then the upper end of the operating li
b. The average distance between the operating line and equilibrium line is large, when the liquidgas ratio is also large in case of a counter current gas
c. The operating line lies above the equilibrium curve in case of a gas desorber
d. With decrease in the liquid flow rate for a fixed gas flow rate, the slope of the operating line decreases, in case of gas absorption process
Answer  Explanation 

ANSWER: The operating line lies above the equilibrium curve in case of a gas desorber

Explanation:
No explanation is available for this question!


3)   Pick out the wrong statement ?

a. Different solids have different equilibrium moisture curves
b. Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillatio
c. Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column
d. Even a forced draft cooling tower cannot cool water below the wet bulb temperature
Answer  Explanation 

ANSWER: Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column

Explanation:
No explanation is available for this question!


4)   Pick out the wrong statement?

a. Packed towers are preferred for vacuum operation, because the pressure drop through the packing is less and they (packings) also lessen the possibilit
b. Packed towers are preferred over plate towers for handling corrosive and foamy liquids
c. Diameter of randomly packed tower is normally more than 1.2 metres
d. Due to uneven supply and improper distribution of liquid, problem of channelling, loading & flooding is generally encountered in packed towers
Answer  Explanation 

ANSWER: Diameter of randomly packed tower is normally more than 1.2 metres

Explanation:
No explanation is available for this question!


5)   Pick out the correct statement?

a. Bound moisture is removed during constant rate drying period
b. Free moisture is removed during falling rate drying period
c. The sum of free moisture and equilibrium moisture in a solid is called the critical moisture
d. The driving force for mass transfer in a wet solid is its free moisture content
Answer  Explanation 

ANSWER: The driving force for mass transfer in a wet solid is its free moisture content

Explanation:
No explanation is available for this question!


6)   Pick out the wrong statement pertaining to leaching ?

a. Fine solids cannot be leached in a Pachuca tank
b. Door classifier can be used for leaching of coarse solids
c. Vegetable seeds can be leached in either of Bollman extractor, Rotocel or Kennedy extractor
d. Very high temperature is not needed for the leaching of sugar beet
Answer  Explanation 

ANSWER: Fine solids cannot be leached in a Pachuca tank

Explanation:
No explanation is available for this question!


7)   Pick out the correct statement ?

a. For identical gas flow rates, less pressure drop occurs through a plate tower than through a packed tower
b. Plate column can handle greater liquid loads without flooding than packed column, but the liquid hold up is more in the case of plate column
c. For the same duty, plate columns weigh less than packed columns
d. All A., B. and C.
Answer  Explanation 

ANSWER: All A., B. and C.

Explanation:
No explanation is available for this question!


8)   Pick out the wrong statement ?

a. With decrease in feed temperature, the number of plates required for binary distillation decreases for a given ‘L/V’ ratio
b. The extraction per unit of total height for a short packed column is more effective than for a tall column, in case of liquid-liquid extraction
c. Natural draft cooling towers are made of ferroconcrete and its cross-section is wider at the bottom
d. Vander wall adsorption is also called chemisorption
Answer  Explanation 

ANSWER: Vander wall adsorption is also called chemisorption

Explanation:
No explanation is available for this question!


9)   Pick out the wrong statement pertaining to the rotary dryer ?

a. Flights (located in the inside shell of rotary dryer) lift the material being dried and shower it down through the current of hot air/gases. It extend
b. Hold up of a rotary drier is defined as the fraction of the dryer volume occupied by the solid at any instant. The best performance for rotary drier i
c. Rotary dryer is suitable for drying sticky material
d. Recommended peripheral speed of a rotary drier is in the range of 10 to 30 metres/minute
Answer  Explanation 

ANSWER: Rotary dryer is suitable for drying sticky material

Explanation:
No explanation is available for this question!


10)   Pick out the correct statement?

a. The slope of the stripping line is always less than unity
b. For a given separation in a binary distillation column, with increase in reflux ratio (above the minimum reflux ratio), the fixed cost of the distilla
c. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux
d. Kremser-Brown-Souder’s equation is used to calculate the efficiency of a plate tower
Answer  Explanation 

ANSWER: In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux

Explanation:
No explanation is available for this question!


11)   Pick out the correct statement ?

a. Dialysis process is used for the production of fresh water from brine
b. Electrodialysis is used in the manufacture of NaOH
c. Electrodialysis is used for the refining/purification of petrol
d. Both B. and C.
Answer  Explanation 

ANSWER: Electrodialysis is used in the manufacture of NaOH

Explanation:
No explanation is available for this question!


12)   Pick out the correct statement ?

a. Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ide
b. A sharp decrease in pressure drop is an indication of flooding in a distillation coloumn
c. Solvent used in extractive distillation should be of high volatility
d. Flash distillation is suitable for separating components which have very close boiling temperature
Answer  Explanation 

ANSWER: Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ide

Explanation:
No explanation is available for this question!


13)   Pick out the wrong statement ?

a. Constant pressure distillation cannot separate an Azeotropic mixture
b. Relative volatility of a binary mixture changes appreciably with the minor change in temperature
c. The relative volatility of a binary mixture at Azeotropic composition is unity
d. Flash distillation is practised on wide spread scale in petroleum refinery
Answer  Explanation 

ANSWER: Relative volatility of a binary mixture changes appreciably with the minor change in temperature

Explanation:
No explanation is available for this question!


14)   Pick out the correct statement ?

a. Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas
b. The ‘Hatta number’ is important in problems involving gas absorption without chemical reaction
c. For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal
d. Total reflux in case of distillation operation requires infinite number of plates for a binary system separation
Answer  Explanation 

ANSWER: For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal

Explanation:
No explanation is available for this question!


15)   Pick out the wrong statement?

a. The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are the same for NSc = NPr= 1
b. 1 Nm3 of dry air is lighter than 1Nm3 of humid air
c. The Lewis number of a mixture is unity, when the thermal diffusivity is equal to the mass diffusivity
d. An Azeotropic mixture of two liquids has boiling point higher than either of them, when it shows negative deviation from Raoult’s Law
Answer  Explanation 

ANSWER: 1 Nm3 of dry air is lighter than 1Nm3 of humid air

Explanation:
No explanation is available for this question!


16)   Pick out the wrong statement ?

a. A horizontal line on the humidity chart indicates the temperature changes at constant molal humidity
b. When water is cooled from 80 to 70°C by exposure to the air with a wet bulb temperature of 60°C, then both the approach & the range would be 10°C
c. For unsaturated air-water vapor mixture at atmospheric conditions, the wet bulb temperature & adiabatic cooling lines are the same
d. Relative saturation of unsaturated mixture of water vapor & air cannot be increased by either reducing the mixture temperature or by increasing the to
Answer  Explanation 

ANSWER: Relative saturation of unsaturated mixture of water vapor & air cannot be increased by either reducing the mixture temperature or by increasing the to

Explanation:
No explanation is available for this question!


17)   Pick out the wrong statement?

a. Change in barometric pressure does not affect the relative humidity
b. In case of a packed tower, the operating velocity is about half of the flooding velocity, generally
c. ‘Elution’ means the desorption of the adsorbed solute by a solvent
d. The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity
Answer  Explanation 

ANSWER: The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity

Explanation:
No explanation is available for this question!


18)   With increase in pressure, the relative volatility for a binary system_________________?

a. Increases
b. Decreases
c. Remains same
d. Either A. or B., depends on the system
Answer  Explanation 

ANSWER: Decreases

Explanation:
No explanation is available for this question!


19)   An example of elution is______________________?

a. Separation of uranium oxide from its ore by H2SO4 in a Pachuca tank
b. Separation of sugar from sugar beet by hot water
c. Dissolution of tannin out of tree barks by water
d. Recovery of vegetable oils from seeds
Answer  Explanation 

ANSWER: Separation of uranium oxide from its ore by H2SO4 in a Pachuca tank

Explanation:
No explanation is available for this question!


20)   If the amount of the steam used in steam distillation is increased, the temperature of distillation__________________?

a. Increases
b. Decreases
c. Remains unchanged
d. Depends on relative volatility
Answer  Explanation 

ANSWER: Decreases

Explanation:
No explanation is available for this question!


21)   Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when____________________?

a. Extracting solvent is cheaply & abundantly available
b. One of the liquid components is heat sensitive
c. Viscosity of liquid components is very high
d. One of the liquid components has very high affinity towards the solvent
Answer  Explanation 

ANSWER: One of the liquid components has very high affinity towards the solvent

Explanation:
No explanation is available for this question!


22)   Separation of two or more components of a liquid solution cannot be achieved by___________________?

a. Fractional crystallisation
b. Liquid extraction
c. Absorption
d. Evaporation
Answer  Explanation 

ANSWER: Absorption

Explanation:
No explanation is available for this question!


23)   In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as_____________________?

a. Ri = Re/(1 – Re)
b. Ri = (1 – Re)/Re
c. Ri = Re
d. Ri = Re/(1 + Re)
Answer  Explanation 

ANSWER: Ri = Re/(1 + Re)

Explanation:
No explanation is available for this question!


24)   For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because__________________?

a. Water has a high latent heat of evaporation
b. Lewis number is close to unity
c. They are always equal under all circumstances
d. Solubility of the components of air in water is very small
Answer  Explanation 

ANSWER: Water has a high latent heat of evaporation

Explanation:
No explanation is available for this question!


25)   If moisture content of solid on dry basis is X, then the same on wet basis is____________________?

a. X/(X + 1)
b. X/(1 – X)
c. (1 + X)/X
d. (1 – X)/X
Answer  Explanation 

ANSWER: X/(X + 1)

Explanation:
No explanation is available for this question!


26)   The-relative volatility for separation of a non-ideal binary mixture by distillation should be ___________________?

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

ANSWER: > 1

Explanation:
No explanation is available for this question!


27)   Which of the following unit operations makes use of Thiele-Geddes equation ?

a. Liquid-liquid extraction
b. Solid-liquid extraction
c. Multi-component absorption with chemical reaction
d. Multi-component distillation
Answer  Explanation 

ANSWER: Multi-component distillation

Explanation:
No explanation is available for this question!


28)   Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent ______________________?

a. A pure component
b. A binary mixture
c. A ternary mixture
d. Partially miscible ternary system
Answer  Explanation 

ANSWER: A binary mixture

Explanation:
No explanation is available for this question!


29)   Air at a particular humidity is heated in a furnace. The new dew point_____________________?

a. Decreases
b. Increases
c. Depends on the extent of heating
d. Remain unchanged
Answer  Explanation 

ANSWER: Increases

Explanation:
No explanation is available for this question!


30)   In case of gases, the binary diffusivity is proportional to (where, P = pressure) ?

a. P
b. 1/P
c. 1/√P
d. √P
Answer  Explanation 

ANSWER: 1/P

Explanation:
No explanation is available for this question!


31)   What is the reflux ratio at total reflux ?

a. Zero
b. Infinity
c. Unity
d. Data insufficient
Answer  Explanation 

ANSWER: Infinity

Explanation:
No explanation is available for this question!


32)   Which of the following is the most suitable for extraction in a system having very low density difference ?

a. Mixer-settler extractor
b. Centrifugal extractor
c. Pulsed extractor
d. Packed extraction tower
Answer  Explanation 

ANSWER: Centrifugal extractor

Explanation:
No explanation is available for this question!


33)   In the desorption of highly soluble gas from the liquid, the main resistance will be in the ______________ phase?

a. Gas
b. Liquid
c. Both A. & B.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Liquid

Explanation:
No explanation is available for this question!


34)   At minimum reflux ratio for a given separation__________________?

a. Number of plates is zero
b. Number of plates is infinity
c. Minimum number of the theoretical plates is required
d. Separation is most efficient
Answer  Explanation 

ANSWER: Number of plates is infinity

Explanation:
No explanation is available for this question!


35)   Diffusion in concentrated solutions differs from that in dilute solutions, because of the change in the _______________ with the concentration of the solution?

a. Degree of ideality
b. Viscosity
c. Both A & B
d. Neither A nor B
Answer  Explanation 

ANSWER: Both A & B

Explanation:
No explanation is available for this question!


36)   The dimension of diffusivity is same as that of the__________________?

a. Density
b. Molal concentration
c. Kinematic viscosity
d. Velocity head
Answer  Explanation 

ANSWER: Kinematic viscosity

Explanation:
No explanation is available for this question!


37)   When the liquid over a plate is of uniform concentration, then ______________________?

a. Murphree efficiency > point efficiency
b. Murphree efficiency < point efficiency
c. Murphree efficiency = point efficiency
d. Murphree efficiency ≠ point efficiency
Answer  Explanation 

ANSWER: Murphree efficiency = point efficiency

Explanation:
No explanation is available for this question!


38)   The term “cooling range” in a cooling tower refers to the difference in the temperature of____________________?

a. Cold water leaving the tower and the wet bulb temperature of the surrounding air
b. Hot water entering the tower and the wet bulb temperature of the surrounding air
c. Hot water entering the tower and the cooled water leaving the tower
d. None of these
Answer  Explanation 

ANSWER: Hot water entering the tower and the cooled water leaving the tower

Explanation:
No explanation is available for this question!


39)   Rate of leaching increases with increasing______________________?

a. Temperature
b. Viscosity of solvent
c. Pressure
d. Size of the solid
Answer  Explanation 

ANSWER: Temperature

Explanation:
No explanation is available for this question!


40)   For _______________ drying, the effects of velocity, temperature and humidity of the gas and the thickness of the solid are the same?

a. Unsaturated surface
b. Constant rate
c. Both A. and B.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Both A. and B.

Explanation:
No explanation is available for this question!