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CHELE > Separation Process > Flashcards

Separation Process 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

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

A

hexane

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5
Q

Leaching of sugar from sugar beets is done using

A

hot water

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6
Q

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

A

decreases

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7
Q

Bollman extractor

A

is used for extraction of oil from oilseed.

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8
Q

Radioactive nuclear waste is treated in

A

pulsed column extractor

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9
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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10
Q

Liquid-liquid extraction is based on the differences in

A

solubility

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11
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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12
Q

The solvent used in liquid extraction should not have high latent
heat of vaporization, because
a. the pressure drop and hence the pumping cost will be very
high.
b. it cannot be recovered by distillation.
c. its recovery cost by distillation may be prohibitively high.
d. it will decompose while recovering by distillation

A

its recovery cost by distillation may be prohibitively high

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13
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.
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.

A

extracting solvent is cheaply & abundantly available

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14
Q

In a counter-current liquid extractor

A

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

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15
Q

A coalescer in a mixer-settler liquid-liquid extraction column
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.
d. all of these

A

d

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16
Q

Antibiotics are best handled in a

A

Podbielniak extractor

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17
Q

Which of the following solutions will follow Raoult’s law most
closely?
a. A solution of benzene, toluene and oxylene
b. 35% solution of camphor in water
c. 35% solution of NH3 in water
d. A solution of polar organic compounds (not of homologs of a
series)

A

a

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18
Q

Boiling point diagram is

A

affected by pressure

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19
Q

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

A

relative volatility

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20
Q

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

A

greatly affected by temperature

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21
Q

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

A

extractive distillation

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22
Q

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

A

Distillation

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23
Q

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

A

lower

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24
Q

Increasing the operating pressure of a distilling column

A

makes separation difficult

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25
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 product composition but not the fraction vaporized.
b. the product composition as well as the fraction vaporized.
c. the fraction vaporized but not the product composition.
d. neither the product composition nor the fraction vaporized.

A

the fraction vaporized but not the product composition

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26
Q

Steam distillation is used to

A

avoid thermal decomposition of a component

27
Q

The amount of steam required per unit quantity of distillate in case
of steam distillation will be reduced by
a. raising the temperature
b. lowering the total pressure
c. both (a) and (b)
d. neither (a) nor (b)

A

c

28
Q

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

A

reflux

29
Q

In a distilling column, the highest pressure will be at

A

bottom

30
Q

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

A

condenser

31
Q

A reboiler provides heat to the

A

the bottom of a distilling column

32
Q

The temperature in distilling column, from bottom to top

A

decreases

33
Q

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

A

infinite number of plates

34
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

35
Q

As the reflux ratio decreases, the

A

number of plates increases.

36
Q

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

A

increases

37
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.
b. mixture (to be separated) shows negative deviation from
ideality.
c. mixture (to be separated) shows positive deviation from
ideality.
d. multicomponent distillation is involved

A

relative volatility is reasonably constant

38
Q

Inside the distillation column, the
a. driving force for the vapor flow is the pressure drop.
b. liquids are not always at their bubble points.
c. pressure increases gradually from bottom to the top of the
column.
d. none of these

A

driving force for the vapor flow is the pressure drop.

39
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

40
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
b. condenser and reboiler surfaces
c. tower cross-section
d. none of these

A

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

41
Q

Overall efficiency of the distillation column is

A

the ratio of number of ideal plates to actual plates

42
Q

Pick out the correct statement.
a. Ponchon-Savarit method is more accurate than McCabeThiele 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

a

43
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

c

44
Q

Design calculation for multiple component distillation is done by

A

tray to tray calculation

45
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

46
Q

In extractive distillation, solvent is
a. added to alter the relative volatility of the mixture.
b. of high volatility.
c. present in overhead stream.
d. of high viscosity to give high tray efficiency.

A

added to alter the relative volatility of the mixture

47
Q

Solvent used in extractive distillation

A

forms a low boiling azeotrope

48
Q

Pick out the wrong statement.
a. Critical moisture content is not a property of the material itself.
b. A sharp increase in pressure drop gives an indication of the
flooding in a distillation column.
c. Separation of components is not possible in liquid extraction, if
selectivity is unity.
d. Dehydration of ethyl alcohol is most economically done by
molecular distillation at very high vacuum.

A

d

49
Q

Azeotropic distillation is employed to separate

A

constant boiling mixture

50
Q

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

A

same

51
Q

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

52
Q

Pick out the system with minimum boiling azeotrope at 1 atm.
a. benzene-toluene c. hydrochloric acid-water
b. ethyl alcohol-water d. all of these

A

c

53
Q

Which of the following binary systems is an example of a
maximum boiling azeotrope?
a. water-hydrochloric acid
b. acetone-carbon disulfide
c. water-ethyl alcohol
d. n-heptane-n-octane

A

c

54
Q

Rose oil is extracted from rose leaves using distillation

A

steam distillation

55
Q

When the solvent dissolves very little of solute then

A

large quantity of solvent is required to extract the solute

56
Q

The triangle whose one corner coincides with the enriching line and the outer corner is on the stripping line is called the

A

feed plate

57
Q

Flash distillation is suitable for the separation of components

A

having very wide boiling points

58
Q

Relative volatility varies with the concentration of component for an ideal solution. The relative volatity of a binary mixture may be defined as the ratio of vapor pressure of component ‘A’ to that of component ‘B’, when
a. only liquid phase obeys Dalton’s law.
b. only vapor phase follows Raoult’s law.
c. liquid phase obeys Dalton’s law and vapor phase obeys Raoult’s law.
d. vapor phase obeys Dalton’s law and liquid phase obeys Raoult’s law.

A

d

59
Q

Leaching of coarse solid lumps is also termed as

A

percolation

60
Q

Large scale usage of flash distillation is practiced in

A

petroleum refining

61
Q

In an operating distillation column, the
a. driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.
b. vapors and liquids are at their dew point and bubble point respectively
c. highest temperature is encountered at the top of the column.
d. driving force for the liquid flow is its specific weight.

A

a

62
Q

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapor, because

a. mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.
b. total pressure is less.
c. saturated steam is used for steam distillation.
d. temperature is less.

A

a

63
Q

For a binary mixture distillation process, the degree of freedom is 2. However, if the pressure is fixed in this process, the number of independent variables in this process will be

A

1

CHELE (17 decks)

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