Mass Transfer Quiz 5

1 / 50

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

1.2 to 1.5

2.5 to 3

3 to 4

2 / 50

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

Sharp drop in pressure drop

Sharp rise in pressure drop

Increase in flow rate

None of these

3 / 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_________?

0.107

0.215

0.017

0.31

4 / 50

In an absorber, HETP does not vary with the______?

Flow rate of gas

Flow rate of liquid

Type and size of packing

None of these

5 / 50

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

Smaller than

Equal to

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

Greater than

6 / 50

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

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

None of these

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

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

7 / 50

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

0.6

0.5

8 / 50

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

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

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

Both A. and B.

9 / 50

In Azeotropic mixture, the equilibrium vapour composition is______?

Independent of pressure

Less than liquid composition

Same as liquid composition

More than liquid composition

10 / 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

Both A. & B.

Straight

11 / 50

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

Dilute solutions and isothermal operation

None of these

Dilute solutions

Isothermal operation

12 / 50

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

X/(1 ? X)

(1 ? X)/X

X/(X + 1)

(1 + X)/X

13 / 50

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

Inverse

Logarithmic

Exponential

Linear

14 / 50

Hypersorption refers to a _________ process?

Fixed bed adsorption

Moving bed absorption

Moving bed adsorption

Fixed bed absorption

15 / 50

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

None of these

Linearly

Inversely

Exponentially

16 / 50

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

-f/(1 ? f)

#NAME?

(1 ? f)/f

? (f ? 1)/f

17 / 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

Both A. & B.

Range is 15?F

Neither A. nor B.

18 / 50

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

None of these

Tower cross-section

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

Condenser and reboiler surfaces

19 / 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 = 0.5 a2

a1 = a2

a1 = 2a2

None of these

20 / 50

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

Depends on relative volatility

Increases

Decreases

Remains unchanged

21 / 50

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

Both A. & B.

Parallel

Straight

Neither A. nor B.

22 / 50

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

Insoluble in the liquid

Soluble in the liquid

Non-ideal in nature

At a fixed temperature

23 / 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.

Both A. and B.

Is one at unity value of

Increases with increase in

24 / 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_____?

G/L

L/G

Always < 1

None of these

25 / 50

In a counter-current liquid extractor_____?

Both liquids can have any desired flow rate

Liquid?s flow rate depends upon the temperature and pressure

Both liquids flow at fixed rate

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

26 / 50

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

Liquid stream should be distributed uniformly

Gas stream should be distributed uniformly

Both gas as well as liquid streams should be distributed uniformly

By passing should be completely avoided

27 / 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.

28 / 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

< 8 : 1

< 6:1

29 / 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 ?

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

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)

Condenser and reboiler loads are the same in both the cases

30 / 50

In an operating distillation column, the________?

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

Driving force for the liquid flow is its specific weight

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

Highest temperature is encountered at the top of the column

31 / 50

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

By passing should be completely avoided Answer: Option C

Liquid stream should be distributed uniformly

Both gas as well as liquid streams should be distributed uniformly

Gas stream should be distributed uniformly

32 / 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 partially miscible liquids

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 an azeotrope

33 / 50

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

Equal to

Lower than

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

Higher than

34 / 50

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

Agitated vessel

Packed tower

Sieve tray column

Bubble cap column

35 / 50

In case of an absorber, the operating ________?

Line always lies above the equilibrium curve

Line always lies below the equilibrium curve

Line can be either above or below the equilibrium curve

Velocity is more than the loading velocity

36 / 50

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

Gas phase

All A , B. & C.

Interface

Liquid phase

37 / 50

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

Decreases

And the heat required in reboiler decreases

Remains unaffected

Increases

38 / 50

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

Remains unchanged

Depends on the pressure of the system

Increases

Decreases

39 / 50

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

Extractive

Molecular

Flash

Azeotropic

40 / 50

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

1.5

-0.6

-1.5

0.6

41 / 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__________?

Gas phase resistance controlled

Liquid phase resistance-controlled

Driven by a non-linear driving force

Impossible

42 / 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

None of these

Relative

Percentage

43 / 50

In case of a desorber (stripper), the_________?

Temperature always increases

Temperature remains unaffected

Operating line always lies above the equilibrium curve

Operating line always lies below the equilibrium curve

44 / 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) ?

6.89

8.89

8.25

45 / 50

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

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

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

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

All A., B. and C.

46 / 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 room temperature

Vapour laden gas at 1 atm. and gas temperature

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

47 / 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

KG = 1/KG + m/KL

KG = 1/KL + m/KG

1/KG = 1/KL + m/KG

48 / 50

None of these

Relative

Molal

Percentage

49 / 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

> 100

None of these

100

50 / 50

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

0.5

> 1

< 1

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