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Reviewer C > Separation Processes Concept > Flashcards

Separation Processes Concept Flashcards

1
Q

A unit operation in which a soluble component is removed from
an inert solid by a solvent which preferentially dissolves the
soluble matter is known as

A

leaching

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2
Q

The unit operation by which soluble components of a liquid
mixture are dissolved in a liquid immiscible with the insoluble
component is

A

solvent extraction

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3
Q

Tea percolation employs

A

leaching

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4
Q

Neem oil is a traditional plant product which possesses
spermicidal properties. A group of students working on their
investigatory project wanted to test how effective the said oil was
as contraceptive by sing it as a component for contraceptives.
The students were able to gather 5 kg of Neem Tree Seeds that
contains 30% of soluble oil and 70% inert solids and they decided
to use 5 kg of pure hexane to extract the oil. What percentage of
oil will they be able to recover given that the ratio of the liquid to
solid components in the underflow is 0.5? Assume ideal
leaching.

A

73 %

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5
Q

Tung meal containing 55% oil is to be extracted at a rate of 4000
kg/hr using n-hexane containing 5% wt oil as solvent. A counter
current multiple stage extraction system is to be used. The meal
retains 2 kg solvent per kg of oil free meal while the residual
charge contains 0.11 kg oil per kg oil free meal while the product
is composed of 15 weight percent of oil. The theoretical number
of stages is

A

4

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6
Q

Which of the following is the most commonly used leaching
solvent in vegetable oil industry?

A

hexane

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7
Q

Leaching of sugar from sugar beets is done using

A

hot water

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8
Q

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

A

decreases

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9
Q

Bollman extractor

A

is used for extraction of oil from oilseed.

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10
Q

Radioactive nuclear waste is treated in

A

pulsed column extractor

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11
Q

Acetic acid will be most economically separated from a dilute
solution of acetic acid in water by

A

solvent extraction

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12
Q

Liquid-liquid extraction is based on the differences in

A

solubility

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13
Q

Which method is more efficient, a single large washing or
repeated small washing?

A

repeated small washing

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14
Q

A solution of solute (A) in diluent (B) is mixed with solvent (S).
The component (B) is slightly soluble in (S). The resulting
extract will be

A

rich in S, poor in B, rich in A

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15
Q

By extraction with amyl acetate, Penicillin F is recovered from an
aqueous fermentation broth using 6 volumes of solvent per 100
volumes of the aqueous phase. At pH = 3.2, the distribution
coefficient KD is 80.
What fraction of the penicillin would be recovered in a single ideal
stage?

A

83%

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16
Q

Benzoic acid is 9 times more soluble in chloroform than in water.
The percent benzoic acid that will remain from a water solution of
benzoic acid if
Equal quantity of chloroform and water is used is

A

10%

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17
Q

The solvent used in liquid extraction should not have high latent
heat of vaporization, because

A

its recovery cost by distillation may be prohibitively high.

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18
Q

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.

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19
Q

In a counter-current liquid extractor

A

only one of the liquids may be pumped at any desired rate.

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20
Q

A coalescer in a mixer-settler liquid-liquid extraction column

A

a. comprises of thin bed of substances of extended surface
having high porosity.
b. helps in increasing the bubble size entering the settler.
c. helps in increasing the settling rate of the bubbles.

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21
Q

Antibiotics are best handled in a

A

Podbielniak extractor

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22
Q

Which of the following solutions will follow Raoult’s law most
closely?

A

A solution of benzene, toluene and oxylene

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23
Q

The percentage change in the boiling point of a 20 mole benzene
– toluene solution when the pressure is increased from 1 atm to
2 atm is

A

25.5 % increase

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24
Q

A 50 % by weight benzene – toluene mixture is fed to a column
at 180 0F and 1 atm. The condition of the feed is called

A

sub cooled liquid

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25
Q

Boiling point diagram is

A

affected by pressure.

26
Q

The ease of difficulty of separating components by distillation is
determined by the

A

relative volatility

27
Q

Strictly speaking, the relative volatility of most ideal binary
solution is

A

greatly affected by temperature

28
Q

When the relative volatility of two miscible components is close to
1.00, the components can be separated by

A

extractive distillation

29
Q

The physical separation of components in a miscible mixture by
simultaneous evaporation and condensation is

A

distillation

30
Q

In a batch distillation, the boiling point of the distillate product
compared to the residue is

A

lower

31
Q

Increasing the operating pressure of a distilling column

A

makes separation difficult

32
Q

One mole feed of a binary mixture of a given composition is flash
vaporized at a fixed P and T. If Raoult’s law is obeyed, then
changing the feed composition would effect

A

the fraction vaporized but not the product composition.

33
Q

Steam distillation is used to

A

avoid thermal decomposition of a component.

34
Q

Glycerin is steam distilled at 1820C and under a 26 in Hg vacuum.
A test shows that one lb of steam is consumed per lb of glycerine
distilled. What percent excess steam is actually used than
theoretical? Vapor pressure of glycerine at 1820C is 21 mmHg.

A

37%

35
Q

The amount of steam required per unit quantity of distillate in case
of steam distillation will be reduced by

A

a. raising the temperature
b. lowering the total pressure

36
Q

In distillation, the cooled liquid stream returned to the column to
a cool plate or stage is called

A

reflux

37
Q

In a distilling column, the highest pressure will be at

A

the bottom

38
Q

A heat transfer equipment to convert vapor to liquid is a/an

A

condenser

39
Q

A reboiler provides heat to the

A

the bottom of a distilling column

40
Q

The temperature in distilling column, from bottom to top

A

decreases

41
Q

If x co-ordinate of intersection point of feed line and rectifying
sections operating line on equilibrium curve is same as the mole
fraction of more volatile components in the feed, then the quality
of feed is

A

saturated liquid

42
Q

The theoretical minimum reflux ratio in distillation column is
attained if the column has

A

infinite number of plates

43
Q

As the reflux ratio decreases, the

A

number of plates increases.

44
Q

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

A

increases.

45
Q

Fenske’s equation for determining the minimum number of
theoretical stages in distillation column holds good, when the

A

relative volatility is reasonably constant.

46
Q

Inside the distillation column, the

A

driving force for the vapor flow is the pressure drop.

47
Q

On moving the feed line (q-line) from saturated liquid feed
(vertical position) to saturated vapor feed (horizontal feed), if the
slope of both the operating lines are to be increased, then it will
result in

A

increased reflux ratio

48
Q

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

A

area between operating line and 45° diagonal x-y diagram

49
Q

Overall efficiency of the distillation column is

A

the ratio of number of ideal plates to actual plates

50
Q

Pick out the correct statement.

a. Ponchon-Savarit method is more accurate than McCabe-
Thiele method to determine the number of theoretical stages

required for the separation of non-ideal binary system by
distillation.
b. A sharp decrease in pressure drop is an indication of flooding
in a distillation column.
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.

A

Ponchon-Savarit method is more accurate than McCabe-
Thiele method to determine the number of theoretical stages

required for the separation of non-ideal binary system by
distillation.

51
Q

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 distillation column first increases and then decreases.
c. In Ponchon-Savarit method of no. of theoretical plate
determination, the stripping and rectifying operating lines are
vertical at total reflux.
d. Kremsor-Brown-Souder’s equation is used to calculate the
efficiency of a plate tower.

A

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

52
Q

Design calculation for multiple component distillation is done by

A

tray to tray calculations

53
Q

Pick out the wrong statement:
a. Reboiler is not used in open steam distillation.
b. The separation of solutes of different molecular sizes in a liquid
solution by use of a suitable membrane is called dialysis.
c. Freeze drying is used for the drying of fish.
d. Fenske-Underwood equation is used for calculating theoretical
number of plates in a distillation column at normal operating reflux
condition.

A

d. Fenske-Underwood equation is used for calculating theoretical
number of plates in a distillation column at normal operating reflux
condition.

54
Q

In extractive distillation, solvent is

A

added to alter the relative volatility of the mixture.

55
Q

Solvent used in extractive distillation

A

forms a low boiling azeotrope.

56
Q

Azeotropic distillation is employed to separate

A

constant boiling mixture

57
Q

The equilibrium liquid composition compared to the vapor
composition in case of azeotropic mixture is

A

same

58
Q
  1. Pick out the wrong statement.
    a. The mole fraction of solute is directly proportional to the
    molality of a ‘dilute’ solution.
    b. For a non-reacting binary mixture of ideal gases, the partial
    pressure distribution of both components is nonlinear in the case
    of steady state unimolal unidirectional diffusion.
    c. Azeotropes obey Raoult’s law at all temperature.
    d. The relative volatility of a binary mixture at the azeotropic
    composition is 1.
A

c. Azeotropes obey Raoult’s law at all temperature.

59
Q

Pick out the system with minimum boiling azeotrope at 1 atm.

A

hydrochloric acid-water

60
Q

Which of the following binary systems is an example of a
maximum boiling azeotrope?

A

water-ethyl alcohol

Reviewer C (19 decks)

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