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Mass Transfer > Test Review > Flashcards

Test Review Flashcards

1
Q

the product of a distillation separation containing the majority of the less volatile components coming from the bottom of the unit

A

bottoms

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2
Q

the ratio of the condensed overhead vapor flow that is returned to the column vs the amount that is taken off as product (L/D)

A

reflux ratio

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3
Q

Order the following from most volatile to least volatile:
propane
i-pentane
n-pentane
methane

A

methane
propane
i-pentane
n-pentane

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4
Q

What are the two state variables you can adjust in flash distillation to change the composition of the product streams?

A

drum pressure and feed temperature

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5
Q

What are the four flow regimes possible in distillation?

A

bubble, foam, froth, and spray

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6
Q

For the light key component, equilibrium relation is
a .yK=x
b. Kx=y
c. depend upon trays
d. cannot be specified

A

Kx=y

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7
Q

If the fractional recovery of light key in the distillate id FR, then the light key in the feed is
a. DxD=(FRD)+FxLK
b. DxD=(FRD)-FxLK
c. DxD=(FRD)FxLK
d. DxD=(FRD)

A

DxD=(FRD)

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8
Q

For multi-component systems, Fenske Method gives
a. minimum reflux
b. minimum strip
c. maximum reflux
d. minimum trays

A

minimum trays

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9
Q

For multi-component systems, Underwood Equations gives
a. minimum reflux
b. minimum strip
c. maximum reflux
d. minimum trays

A

minimum reflux

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10
Q

The component balance of the more volatile component is given as
a. FzF=DxD+BxB
b. FzF=DxD-BxB
c. FzF=DxD/BxB
d. FzF=DxD*BxB

A

FzF=DxD+BxB

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11
Q

A pinch point may occur at intersection of feed line and
a. stream line
b. stripping line
c. rectifying line
d. equilibrium line

A

equilibrium line

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12
Q

The real number of trays are obtained as a ratio of
a. number of ideal trays and flow rate
b. number of ideal trays and efficiency
c. number of ideal trays and reflux ratio
d. number of ideal trays and stripping ratio

A

number of ideal trays and efficiency

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13
Q

Which of the following is an important assumption of McCabe Thiele method?
a. heat loss is maximum
b. heat loss is negligible
c. heat loss is infinite
d. cannot be specified

A

heat loss is negligible

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14
Q

Which is a proper form of Henry’s Law?
a. Ptot=Hbxb
b. yb=Hbxb
c. yb=Hb/xb
d. Pb=Hb*xb

A

Pb=Hb*xb

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15
Q

Which is represented by the figure?(operating line over equilibrium line)
a. stripper
b. scrubber
c. heat exchanger
d. three-phase extractor

A

scrubber

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16
Q

Which is represented by the figure? (equilibrium over operating line)
a. stripper
b. scrubber
c. heat exchanger
d. three-phase extractor

A

stripper

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17
Q

A scrubber is designed to
a. remove contaminant from liquid phase
b. remove contaminant from gas phase
c. separate two liquids
d. dissolve solid in gas phase

A

remove contaminant from gas phase

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18
Q

A stripper is designed to
a. remove contaminant from liquid phase
b. remove contaminant from gas phase
c. separate two liquids
d. dissolve solid in gas phase

A

remove contaminant from liquid phase

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19
Q

How many trays are represented in the drawing?
a. 0
b. 1
c. 2
d. 3
______
____l

A

2

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20
Q

T or F: Because the enriching section of a distillation column has higher concentrations of the less volatile product in it, it tends to be the cooler portion of a distillation system.

A

False

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21
Q

T or F: For a distillation column, the lower the reflux ratio, the lower the utility costs for proper operation.

A

True

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22
Q

If the vapor pressure of the two components in a binary mixture is same, then it is a _____
a. isotope
b. azeotrope
c. differential boiling point
d. none of the mentioned

A

azeotrope

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23
Q

The use of vapor produced from the reboiler is ____
a. to strip out more volatile component from liquid
b. to strip out less volatile component from the liquid
c. to increase the temperature of the fractionator bottom
d. none of the mentioned

A

to strip out more volatile component from liquid

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24
Q

The reflux of liquid produced from the condenser is ___
a. to strip out more volatile component from vapor
b. to strip out less volatile component from the vapor
c. to decrease the temperature of the fractionator top
d. none of the mentioned

A

to strip out less volatile component from the vapor

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25
Q

If the feed enters the distillation column at its dew point, then the slope of the feed line is _____
a. infinity
b. 0
c. 1
d. between 0 and 1

A

1

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26
Q

If the feed enters the distillation column at its boiling point, then the slope of the feed line is ____
a. infinity
b. 0
c. 1
d. between 0 and 1

A

infinity

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27
Q

Raising the column pressure results in ____
a. lower relative volatility
b. higher relative volatility
c. no effect
d. decreased throughput

A

lower relative volatility

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28
Q

The slope of the top operating line in distillation is:
a. V/L
b. L/V
c. Vbar/Lbar
d. Lbar/Vbar

A

L/V

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29
Q

The phenomena of the flowing liquid toward the wall of tower and dispersed in lateral direction is called ___
a. channeling
b. flow casting
c. entraining
d. regimens

A

channeling

30
Q

T or F: Flux is in the opposite direction to the direction of the increasing concentration gradiant

A

True

31
Q

T or F: For a system containing A and B only, steady state equimolar counter diffusion requires that the flux of a is the negative of the flux of B

A

true

32
Q

T or F: In a typically used industrial distillation column, the liquid surface is boiling violently and is well mixed which is not true for the vapor phase.

A

True

33
Q

Distillation is possible only of the solution components are ___
a. volatile
b. non-volatile
c. cryogenic
d. none of the mentioned

A

volatile

34
Q

The light key components are ____
a. more volatile
b. less volatile
c. non volatile
d. none of the mentioned

A

more volatile

35
Q

The heavy key components are ____
a. more volatile
b. less volatile
c. non volatile
d. none of the mentioned

A

less volatile

36
Q

At total reflux,
a. residue is 0
b. distillate is 0
c. reflux is 0
d. all of the mentioned

A

distillate is 0

37
Q

Gilliland Correlation is arranged to estimate the ___
a. numbers of stages
b. numbers of reboiler
c. numbers of feed
d. numbers of column

A

numbers of stages

38
Q

Once the components are identified, in a multicomponent distillation they are called ___
a. key components
b. mixed components
c. flow components
d. gain components

A

key components

39
Q

At minimum reflux, number of stages is
a. unity
b. infinite
c. minimized
d. negative

A

infinite

40
Q

Which of the following is true for Fick’s law?
a. used to determine the steady-state flux of a component
b. relies on time-dependence of concentration
c. predicts molecular flow from low to high concentration
d. only reliable at low temperatures and high pressures

A

used to determine the steady-state flux of a component

41
Q

In a binary system, the higher the concentration of the less volatile species in the feed to a flash drum:
a. the higher the liquid flow rate leaving the drum
b. the higher the vapor flow rate leaving the drum
c. the larger the flash drum
d. cannot determine

A

The higher the liquid flow rate leaving the drum

42
Q

The relative volatility of components i and k can be defined as:
a. Ki/Kj
b. K/Kj
c. yi/y
d. xi/x

A

Ki/Kj

43
Q

The energy balance around a distillation column is given by:
a. FhF + Qc + Qr = DhD + BhB
b. FhF - Qc + Qr = DhD + BhB
c. V1H1 + Qc = L0h0 + DhD
d. V1H1 - Qc = L0h0 + DhD

A

FhF + Qc + Qr = DhD + B*hB

44
Q

The material balance around the condenser is given by:
a. F = D - B
b. F = D + B
c. V = L + D
d. V = L - D

A

V = L + D

45
Q

The reflux ratio can be defined as:
a. V/L
b. D/L
c. V/B
d. L/D

A

L/D or L0/d

46
Q

The intercept of the bottom operating line in distillation is:
a. Lbar/Vbar
b. Vbar/Lbar
c. 1 - Lbar/Vbar
d. 1 + Lbar/Vbar

A

1 - Lbar/Vbar

47
Q

HETP stands for:
a. height of efficient total packing
b. height equivalent to theoretical plate
c. height expected to product
d. high energy thermal plasma

A

height equivalent to theoretical plate

48
Q

Column diameter is most dependent on:
a. tray type used
b. reboiler duty
c. liquid velocity
d. vapor velocity

A

vapor velocity

49
Q

Which of the following is used when determining tray spacing?
a. propensity of liquid to foam/entrain
b. need for person to access top of trays
c. a&b
d. none of the above

A

propensity of liquid to foam/entrain
need for person to access top of trays

50
Q

In steady state diffusion, which of the following remains constant?
a. concentration gradient
b. kinetic energy of particles
c. potential energy of particles
d. change of concentration with respect to temperature

A

concentration gradient

51
Q

Which of the following is not a part of Fick’s first law at steady-state?
a. diffusion flux
b. diffusion coefficient
c. change in concentration with respect to position in space
d. change in concentration with respect to time

A

change in concentration with respect to time

52
Q

The higher the concentration of volatile species in the feed to a flash drum:
a. the higher the liquid flow rate
b. the higher the vapor flow rate
c. the larger the flash drum
d. cannot determine

A

the higher the vapor flow rate

53
Q

For multi-component flash distillation, the equation used for iterative solving is the
a. Michaelis-Menten
b. Monod
c. Van der Waals
d. Rachford-Rice

A

Rachford-Rice

54
Q

The overall material balance for a distillation column is:
a. F = D - B
b. F = D + B
c. V = L + D
d. V = L - D

A

F = D + B

55
Q

When heat is supplied to bottom of liquid stage to vaporize a portion, it is called:
a. condensing
b. boil-up
c. cooling
d. desalting

A

boil-up

56
Q

When a portion of the overhead product is returned to the column, it is called:
a. reflux
b. dew point
c. boil-up
d. relative BP

A

reflux

57
Q

The energy balance around the condenser is given by:
a. FhF + Qc + Qr = DhD + BhB
b. FhF - Qc + Qr = DhD + BhB
c. V1H1 + Qc = L0h0 + DhD
d. V1H1 - Qc = L0h0 + DhD

A

V1H1 + Qc = L0h0 + D*hD

58
Q

The quality of feed represents:
a. The fraction of liquid in the feed
b. The fraction of vapor in the feed
c. The apparent fraction of liquid in the feed
d. The apparent fraction of vapor in the feed

A

The apparent fraction of liquid in the feed

59
Q

The fraction of the feed represents:
a. The fraction of liquid in the feed
b. The fraction of vapor in the feed
c. The apparent fraction of liquid in the feed
d. The apparent fraction of vapor in the feed

A

The apparent fraction of vapor in the feed

60
Q

Which of the following is NOT necessarily true for Constant Molar Overflow?
a. the volume flows are constant
b. the molar flows are constant
c. the heat of vaporization is constant between stages
d. the heat capacity is constant between stages

A

the volume flows are constant

61
Q

Total reflux condition at steady-state means that:
a. D = 0
b. B = 0
c. F = 0
d. all of the above

A

D = 0, B = 0, F = 0

62
Q

Minimum reflux is the point where:
a. reflux is zero
b. bottoms flow is maximized
c. the separation can be completed with an infinite number of stages
d. reflux = distillate

A

the separation can be completed with an infinite number of stages

63
Q

process of separating components based on differences in volatility

A

distillation

64
Q

product of a distillation separation containing the majority of the more volatile components coming from the top of the unit

A

distillate

65
Q

What is the location of the condenser in the figure?
a. P
b. R
c. S
d. no condenser
(top of operating line)

A

P

66
Q

The point where the operating line and the equilibrium line meet in distillation methods is known as ___
a. plait point
b. Q point
c. pinch point
d. none of the mentioned

A

pinch point

67
Q

Which of the following is always true for equimolar diffusion with any two components (A&B)?
a. dCA/dt = dCB/dt
b. JA = -JB
c. MWA = MWB
d. TA = -TB

A

JA = -JB

68
Q

The value of Ki can be expressed as:
a. yj/xi
b. yi/xj
c. xi/yi
d. yi/xi

A

yi/xi

69
Q

As a rule of thumb, the overall efficiency is:
a. 0.1 to 0.3
b. 0.3 to 0.5
c. 0.5 to 0.7
d. 0.7 to 0.9

A

0.5 to 0.7

70
Q

When sizing a column, switching for trays to packing usually results in:
a. increased height
b. decreased height
c. no change in height
d. no change in trend

A

decreased height

71
Q

Which of the following law is used for steady state diffusion?
a. Fick’s Law
b. Newton’s Law of Diffusion
c. Bragg’s Law
d. Charles’s Law

A

Fick’s Law

72
Q

The overall material balance for a flash drum is:
a. F = V - L
b. F = V/L
c. F = V + L
d. F = F * L

A

F = V + L

Mass Transfer (7 decks)

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