Mass Transfer Quiz 5

1 / 50

In a forced draft cooling tower, water is cooled from 95 to 80?F by exposure to air with a wet bulb temperature of 70?F. In this case, the__________?

Approach is 10?F

Range is 15?F

Neither A. nor B.

Both A. & B.

2 / 50

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

(1 + X)/X

X/(X + 1)

(1 ? X)/X

X/(1 ? X)

3 / 50

In case of _______ distillation, a solvent is added to alter the relative volatility of the mixture to be separated?

Flash

Azeotropic

Molecular

Extractive

4 / 50

In an interphase mass transfer process, the lesser the solubility of a given solute in a liquid, the higher are the chances that the transfer process will be__________?

Driven by a non-linear driving force

Gas phase resistance controlled

Liquid phase resistance-controlled

Impossible

5 / 50

If the overall efficiency and Murphree plate efficiency are equal, then both the equilibrium and operating lines are________?

Both A. & B.

Neither A. nor B.

Parallel

Straight

6 / 50

In a gas-liquid absorption column, for obtaining the maximum absorption efficiency______?

Gas stream should be distributed uniformly

Both gas as well as liquid streams should be distributed uniformly

Liquid stream should be distributed uniformly

By passing should be completely avoided Answer: Option C

7 / 50

In a moderately sized packed absorption tower, channelling (which is most severe with stacked packings) can be minimised by taking the ratio of tower diameter to packing diameter ?

< 8 : 1

> 4 :1

< 6:1

> 8:1

8 / 50

If a two phase system is in physical equilibrium; then it means that, the_______?

All A., B. and C.

Escaping tendency of each component from the liquid phase to the vapor phase is exactly equal to that from vapor phase to liquid phase

Temperature of the liquid phase is equal to that of the vapor phase

Total pressure throughout the liquid phase is equal to that throughout the vapor phase

9 / 50

In an absorber, HETP does not vary with the______?

None of these

Flow rate of liquid

Type and size of packing

Flow rate of gas

10 / 50

In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of_________?

Tower cross-section

None of these

Area between operating line and 45? diagonal x-y diagram

Condenser and reboiler surfaces

11 / 50

In a distillation column, with increase in the reflux ratio, the heat removed in the cooler ________?

Increases

And the heat required in reboiler decreases

Decreases

Remains unaffected

12 / 50

If f = moles of vapour present per mole of feed, then the slope of feed line is (McCabe- Thiele method) __________?

(1 ? f)/f

-f/(1 ? f)

#NAME?

? (f ? 1)/f

13 / 50

In a binary system, separation is very efficient, when the relative volatility is________?

> 1

0.5

< 1

14 / 50

If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that_____?

The system comprises of miscible liquids

On heating, a vapor phase will appear; while on cooling, a solid phase will appear

The system comprises of partially miscible liquids

The system comprises of an azeotrope

15 / 50

In an operating distillation column, the________?

Vapors and liquids are at their dew point and bubble point respectively

Driving force for the liquid flow is its specific weight

Highest temperature is encountered at the top of the column

Driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column

16 / 50

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?

Molal

Percentage

None of these

Relative

17 / 50

In case of a desorber (stripper), the_________?

Temperature always increases

Operating line always lies below the equilibrium curve

Temperature remains unaffected

Operating line always lies above the equilibrium curve

18 / 50

In a gas-liquid absorption column, for obtaining the maximum absorption efficiency_____?

Gas stream should be distributed uniformly

Liquid stream should be distributed uniformly

By passing should be completely avoided

Both gas as well as liquid streams should be distributed uniformly

19 / 50

In Azeotropic mixture, the equilibrium vapour composition is______?

Same as liquid composition

More than liquid composition

Less than liquid composition

Independent of pressure

20 / 50

If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be ________ percent?

< 100

None of these

> 100

100

21 / 50

Humid volume is the total volume in m3 of 1 kg of _______?

Vapour laden gas at 1 atm. and room temperature

Gas plus its accompanying vapour at 1 atm. and gas temperature

Gas plus its accompanying vapour at 1 atm. and room temperature

Vapour laden gas at 1 atm. and gas temperature

22 / 50

In case of absorption, both the operating and equilibrium lines will be straight for_______?

Isothermal operation

None of these

Dilute solutions and isothermal operation

Dilute solutions

23 / 50

If the amount of the steam used in steam distillation is increased, the temperature of distillation___________?

Decreases

Remains unchanged

Depends on relative volatility

Increases

24 / 50

Relative

Percentage

None of these

Molal

25 / 50

If G = insoluble gas in gas stream and L = non-volatile solvent in liquid stream, then the slope of the operating line for the absorber is_____?

Always < 1

L/G

G/L

None of these

26 / 50

Hydrogenation of oil is carried out in a/an ________ in Vanaspati manufacturing plant?

Sieve tray column

Packed tower

Bubble cap column

Agitated vessel

27 / 50

If xD = overhead product molal composition and RD = reflux ratio, then slope and intercept of the operating line for rectifying section are respectively ?

None of these

[xD/(RD + 1)], [(RD + 1)/RD]

[RD/(RD + 1)], [xD/(xD + 1)]

[xD/(RD + 1)], [RD/(RD + 1)]

28 / 50

Humid volume, at a given temperature is a/an ________ function of humidity?

Linear

Logarithmic

Exponential

Inverse

29 / 50

In case of an absorber, the operating ________?

Line can be either above or below the equilibrium curve

Velocity is more than the loading velocity

Line always lies above the equilibrium curve

Line always lies below the equilibrium curve

30 / 50

In case of constant underflow extraction operation, the _________ at all solute concentration?

Ratio of the insoluble to solution is constant

Both A. & B.

Solids are drained to the same extent

Neither A. nor B.

31 / 50

Hypersorption refers to a _________ process?

Moving bed absorption

Fixed bed absorption

Moving bed adsorption

Fixed bed adsorption

32 / 50

In case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of ________ is zero?

Liquid phase

Interface

All A , B. & C.

Gas phase

33 / 50

If Rm is the minimum reflux ratio, the optimum reflux ratio may be around __________ Rm ?

1.2 to 1.5

3 to 4

2.5 to 3

34 / 50

In case of absorption with exothermic reaction, for fluids having _____?

Both A. and B.

Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same

Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence

Pr = Sc; there won?t be any change in heat and mass transfer flux with changes in degree of turbulence

35 / 50

In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of__________?

0.6

-0.6

-1.5

1.5

36 / 50

If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement ?

a1 = 2a2

a1 = 0.5 a2

a1 = a2

None of these

37 / 50

In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as _____ ?

1/KG = 1/KG + m/KL

1/KG = 1/KL + m/KG

KG = 1/KL + m/KG

KG = 1/KG + m/KL

38 / 50

In an absorption column, the flooding velocity for random packing is _____ that for stacked/regular packing?

Greater than

Either A., or B.; depends on the type of packing

Smaller than

Equal to

39 / 50

In case of an unsaturated mixture of gas and vapor, the percentage saturation is ___________ its relative saturation?

Equal to

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

Higher than

Lower than

40 / 50

In case of an ideal solution, the total vapor pressure varies _______ with the composition expressed as mole fraction?

Linearly

None of these

Inversely

Exponentially

41 / 50

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 ?

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

Both condenser and reboiler loads are higher in case (ii) as compared to case (i)

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

Condenser and reboiler loads are the same in both the cases

42 / 50

In a counter-current liquid extractor_____?

Liquid?s flow rate depends upon the temperature and pressure

Only one of the liquids may be pumped at any desired rate

Both liquids flow at fixed rate

Both liquids can have any desired flow rate

43 / 50

If the specific heats of a gas and a vapor are 0.2KJ/Kg.?K and 1.5 KJ/Kg.?K respectively, and the humidity is 0.01; the humid heat in KJ/?Kg. is_________?

0.31

0.017

0.107

0.215

44 / 50

In a packed absorption tower, if the equilibrium and operating lines are both straight lines, then the ratio, HETP/HTUOG _______ the absorption factor?

Neither A. nor B.

Is one at unity value of

Increases with increase in

Both A. and B.

45 / 50

In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is_________?

0.6

0.5

46 / 50

In a packed tower, the value of HETP equals HTUOG, when the equilibrium and the operating lines are (where, HETP = height equivalent to a theoretical plate HTUOG = overall gas phase height of a transfer unit) ?

Neither A. nor B.

Parallel

Straight

Both A. & B.

47 / 50

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) ?

8.25

8.89

6.89

48 / 50

In a packed bed absorption column, the channelling will be noted by the ______?

Increase in flow rate

Sharp drop in pressure drop

None of these

Sharp rise in pressure drop

49 / 50

In a counter-current extractor, as the axial mixing increases, the extraction efficiency________?

Remains unchanged

Increases

Depends on the pressure of the system

Decreases

50 / 50

Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is_____?

Insoluble in the liquid

Non-ideal in nature

Soluble in the liquid

At a fixed temperature

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