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Day 2 > DISTILLATION > Flashcards

DISTILLATION Flashcards

1
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. A solution of benzene, toluene and oxylene

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2
Q

A binary mixture of two moles benzene and 8 moles of toluene
will boil at
a. 110 0C c. 110 0F
b. 105 0C d. 102 0C

A

d. 102 0C

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3
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. saturated liquid c. saturated vapor
b. sub cooled liquid d. mixture of liquid and vapor

A

b. sub cooled liquid

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4
Q

Boiling point diagram is
a. not affected by pressure.
b. affected by pressure.
c. a plot of temperature vs. liquid composition.
d. a plot of temperature vs. vapor composition.

A

b. affected by pressure.

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5
Q

The ease of difficulty of separating components by distillation is
determined by the
a. relative volatility c. mole fraction
b. viscosity d. weight fraction of the components

A

a. relative volatility

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6
Q

Strictly speaking, the relative volatility of most ideal binary
solution is
a. not affected by temperature
b. greatly affected by temperature
c. slightly affected by temperature
d. greatly affected by pressure

A

b. greatly affected by temperature

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7
Q

When the relative volatility of two miscible components is close to
1.00, the components can be separated by
a. simple rectification c. extractive distillation
b. batch distillation d. flash distillation

A

c. extractive distillation

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8
Q

The physical separation of components in a miscible mixture by
simultaneous evaporation and condensation is
a. absorption c. extraction
b. drying d. distillation

A

d. distillation

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9
Q

In a batch distillation, the boiling point of the distillate product
compared to the residue is
a. the same c. lower
b. higher d. half

A

c. lower

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10
Q

Increasing the operating pressure of a distilling column
a. does not make a difference in components separation
b. makes separation difficult
c. sharpens separation
d. requires less heat in the feed heater

A

b. makes separation difficult

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11
Q

Steam distillation is used to
a. reduce the number of plates.
b. avoid thermal decomposition of a component.
c. increase the efficiency of separation.
d. increase the total pressure of distillation

A

b. avoid thermal decomposition of a component.

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12
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. both (a) and (b)

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13
Q

In distillation, the cooled liquid stream returned to the column to
a cool plate or stage is called
a. reboil c. feed
b. reflux d. bottoms

A

b. reflux

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14
Q

In a distilling column, the highest pressure will be at
a. the top
b. the bottom
c. the feed plate
d. between the feed plate and the top

A

b. the bottom

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15
Q

A heat transfer equipment to convert vapor to liquid is a/an
a. evaporator c. condenser
b. reboiler d. still

A

c. condenser

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16
Q

A reboiler provides heat to the
a. top
b. the feed
c. the intermediate reflux
d. the bottom of a distilling column

A

d. the bottom of a distilling column

17
Q

The temperature in distilling column, from bottom to top
a. increases
b. maximum
c. decreases
d. between minimum & maximum

A

c. decreases

18
Q

The theoretical minimum reflux ratio in distillation column is
attained if the column has
a. 1 plate c. 100 plates
b. 10 plates d. infinite number of plates

A

d. infinite number of plates

19
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. subcooled liquid c. saturated liquid
b. saturated vapor d. superheated vapor

A

c. saturated liquid

20
Q

As the reflux ratio decreases, the
a. separation becomes more efficient.
b. number of plates increases.
c. column diameter increases.
d. none of these.

A

b. number of plates increases.

21
Q

In a distillation column, with increase in the reflux ratio, the heat
removed in the cooler
a. increases.
b. decreases.
c. remains unaffected.
d. and the heat required in reboiler decreases.

A

a. increases.

22
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

a. relative volatility is reasonably constant.

23
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

a. driving force for the vapor flow is the pressure drop.

24
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. greater degree of separation with a fixed number of trays
b. increased reboiler load
c. increased reflux ratio
d. none of these

A

c. increased reflux ratio

25
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

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

26
Q

Overall efficiency of the distillation column is
a. the ratio of number of ideal plates to actual plates
b. the ratio of number of actual plates to ideal plates
c. same as the Murphree efficiency
d. always more than the point efficiency

A

a. the ratio of number of ideal plates to actual plates

27
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

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.

28
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. In Ponchon-Savarit method of no. of theoretical plate
determination, the stripping and rectifying operating lines are
vertical at total reflux.

29
Q

Design calculation for multiple component distillation is done by
a. Ponchon-Savarit method
b. Mccabe-Thiele method
c. enthalpy concentration method
d. tray to tray calculations

A

d. tray to tray calculations

30
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.

31
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

a. added to alter the relative volatility of the mixture.

32
Q

Solvent used in extractive distillation
a. is of low volatility.
b. forms a low boiling azeotrope.
c. forms a high boiling azeotrope.
d. does not alter the relative volatility of the original components

A

b. forms a low boiling azeotrope.

33
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. Dehydration of ethyl alcohol is most economically done by
molecular distillation at very high vacuum.

34
Q

Azeotropic distillation is employed to separate
a. constant boiling mixture
b. high boiling mixture
c. mixture with very high relative volatility
d. heat sensitive materials

A

a. constant boiling mixture

35
Q
  1. The equilibrium liquid composition compared to the vapor
    composition in case of azeotropic mixture is
    a. more
    b. less
    c. same
    d. either more or less; depends on the system
A

c. same

36
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. Azeotropes obey Raoult’s law at all temperature.

37
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. hydrochloric acid-water

38
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. water-ethyl alcohol

Day 2 (9 decks)

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