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Philippine Chemical Engineering Licensure Examination Day 2 Separation Processes > IndiaBIX Chemical Engineering: Mass Transfer Section 5 > Flashcards

IndiaBIX Chemical Engineering: Mass Transfer Section 5 Flashcards

1
Q

Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when
extracting solvent is cheaply & abundantly available.
one of the liquid components is heat sensitive.
viscosity of liquid components is very high.
one of the liquid components has very high affinity towards the solvent.

A

one of the liquid components has very high affinity towards the solvent.

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2
Q

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

A

driving force for the vapour flow is the pressure drop.

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3
Q

Diffusivity in concentrated solutions differs from that in dilute solutions, because of the changes in
viscosity with concentration.
degree of ideality of the solution.
both (a) and (b).
neither (a) nor (b).

A

both (a) and (b).

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4
Q

Occurrence of ‘case hardening’ during drying of a high moisture solid cake __________ the drying rate.
increases
decreases
does not affect
exponentially increases

A

decreases

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5
Q

Which of the following is not a continuous drier ?
Drum drier
Spray drier
Tunnel drier
Tray drier

A

Tray drier

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6
Q

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

A

insoluble in the liquid

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7
Q

__________ is the temperature at which a gas-vapor mixture becomes saturated, when cooled at constant total pressure out of contact with a liquid.
Dew point
Bubble point
Dry bulb temperature
Wet bulb temperature

A

Dew point

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8
Q

Rate of leaching increases with increasing
temperature
viscosity of solvent
pressure
size of the solid

A

temperature

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9
Q

An azeotropic mixture is a __________ mixture.
binary
ternary
constant boiling point
none of these

A

constant boiling point

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10
Q

Pick out the wrong statement.
In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed.
In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency.
For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10-2m/s. Then the average mass transfer co-efficient for the plate is 2 x 10-2m/s.
The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity.

A

For Laminar flow over a plate of length L, the local mass transfer co-efficient at a distance L from the leading edge is 1.5 x 10

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11
Q

Molecular seives are regenerated by heating to __________ °C.
< 150
200-330
> 500
> 1000

A

200-330

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12
Q

In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as
Ri = Re/(1-Re)
Ri = (1-Re)/Re
Ri = Re
Ri = Re/(1+Re)

A

Ri = Re/(1+Re)

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13
Q

In a counter-current extractor, as the axial mixing increases, the extraction efficiency
increases
decreases
remains unchanged
depends on the pressure of the system

A

decreases

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14
Q

Heat sensitive materials like certain pharmaceuticals and food stuffs can be dried in a/an __________ dryer.
indirect tray
spray
freeze
none of these

A

freeze

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15
Q

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

A

added to alter the relative volatility of the mixture.

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16
Q

Radioactive nuclear waste is treated in
mixer-settler extractor
rotating-disc contactor
pulsed column extractor
Bollman extractor

A

pulsed column extractor

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17
Q

Large scale drying of sugar is done in a __________ dryer.
spouted bed
tray
rotary
truck

A

rotary

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18
Q

__________ temperature is the steady state temperature attained by a small amount of liquid evaporating into a large quantity of unsaturated gas-vapor mixture.
Dry bulb
Wet bulb
Dew point
none of these

A

Wet bulb

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19
Q

The drying time between fixed moisture contents within the ‘constant rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid )
sqrt(T)
T
T^1.5
T^3

A

T

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20
Q

__________ equation applies to diffusivities in liquids.
Gilliland
Hirschfelder
Wilke and Chang
none of these

A

Gilliland

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21
Q

A packed tower compared to a plate tower for a particular mass transfer operation
incurs smaller pressure drop.
allows installation of cooling coils.
is less costly when built in large sizes/diameters.
is more suitable, if suspended solids are present in fluid streams.

A

incurs smaller pressure drop.

22
Q

Which of the following is the most commonly used leaching solvent in vegetable oil industry ?
Phenol
Hexane
Furfurol
Liquid SO2

A

Hexane

23
Q

In an absorber, HETP does not vary with the
flow rate of liquid
flow rate of gas
type and size of packing
none of these

A

none of these

24
Q

Large quantity of silica gel is normally dried in a __________ dryer.
freeze
through circulation
rotary vacuum
tray

A

through circulation

25
Q

For the same system, if the same liquid used in an absorber is decreased, the tower height will
increase
decrease
remain unaffected
decrease or increase ; depends on the type of liquid

A

increase

26
Q

Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant.
agitated vessel
sieve tray column
bubble cap column
packed tower

A

agitated vessel

27
Q

Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent
a pure component.
a binary mixture.
a ternary mixture.
partially miscible ternary system.

A

a binary mixture.

28
Q

In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when
saturated feed is not used.
an azeotrope forms.
the latent heat of vaporisation of the more and less volatile components are greatly different.
a total condenser is used.

A

a total condenser is used.

29
Q

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
liquid phase resistance-controlled.
gas phase resistance controlled.
impossible.
driven by a non-linear driving force.

A

gas phase resistance controlled.

30
Q

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

A

number of plates increases.

31
Q

Which of the following equipments is not used for gas dispersion ?
Agitated vessels
Bubble cap tray towers
Perforated sieve tray towers
Spray towers

A

Spray towers

32
Q

One mole feed of a binary mixture of a given composition is flash vaporised at a fixed P and T. If Raoult’s law is obeyed, then changing the feed composition would effect
the product composition but not the fraction vaporised.
the product composition as well as the fraction vaporised.
the fraction vaporised but not the product composition.
neither the product composition nor the fraction vaporised.

A

the fraction vaporised but not the product composition.

33
Q

The equation, NA = (DAB * Pt / R * T *Z) * (y1 - y2) is for
steady state equimolar counter diffusion
Fick’s first law of diffusion
steady state diffusion for stagnant case
liquid M.T.C. by penetration theory.

A

steady state equimolar counter diffusion

34
Q

With increase in the liquid flow rate at a fixed gas velocity in a randomly packed counter current gas-liquid absorption column, the gas pressure drop
decreases
remains unchanged
increases
decreases exponentially

A

increases

35
Q

The equation, NA = (DAB * Pt / R * T *Z * PBM) * (PA1 - PA2) is for
Fick’s second law of diffusion.
stready state diffusion for stagnant case.
liquid M.T.C. by Higbie penetration theory.
none of these.

A

stready state diffusion for stagnant case.

36
Q

Which of these columns incurs the lowest pressure drop ?
Packed column (with stacked packing)
Packed column (with dumped packing)
Bubble plate column
Pulse column

A

Packed column (with stacked packing)

37
Q

In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase.
gas
liquid
both (a) & (b)
neither (a) nor (b)

A

liquid

38
Q

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
L/G
G/L
always < 1
none of these

A

L/G

39
Q

Which of the following remains constant during evaporative cooling process with recirculated water supply ?
Relative humidity
Partial pressure of vapour
Wet bulb temperature
None of these

A

Wet bulb temperature

40
Q

For stripping of a gas in a counter current stripper, the operating line
lies above the equilibrium curve.
lies below the equilibrium curve.
can lie above or below the equilibrium curve.
is always parallel to the equilibrium curve.

A

can lie above or below the equilibrium curve.

41
Q

Which of the following same diameter columns gives lowest pressure drop per unit height ?
Bubble-cap column
Sieve-plate column
Packed column (stacked)
Randomly packed column

A

Packed column (stacked)

42
Q

Diffusion in concentrated solutins differs from that in dilute solutions, because of the change in the __________ with the concentration of the solution.
degree of ideality
viscosity
both ‘a ‘& ‘b’
neither ‘a’ nor ‘b’

A

both ‘a ‘& ‘b’

43
Q

Stage efficiency in a leaching process depends on the
time of contact between the solid and the solution
rate of diffusion of the solute through the solid and into the liquid
both (a) and (b)
vapour pressure of the solution

A

both (a) and (b)

44
Q

Operating velocity in a packed tower is usually __________ the flooding velocity.
half
twice
equal to
more than

A

half

45
Q

The Knudsen diffusivity is dependent on the
molecular velocity only.
pore radius of the catalyst only.
molecular mean free path only.
molecular velocity and por radius of the catalyst.

A

molecular velocity and por radius of the catalyst.

46
Q

Minimum possible diameter of a packed coloumn is decided mainly by the
flooding
gas viscosity
liquid density
liquid hold up

A

flooding

47
Q

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

A

forms a low boiling azeotrope.

48
Q

Capacity of a rotary dryer depends on its
r.p.m
inclination with ground surface
both (a) and (b)
neither (a) nor (b)

A

both (a) and (b)

49
Q

The cooling effect in a cooling tower can be speeded up by
increasing the air velocity and area of exposed wet surface.
reducing the barometric pressure.
reducing the humidity of the air.
all (a), (b) and (c).

A

all (a), (b) and (c).

50
Q

he following plot gives the saturated humidity (He) versus temperature (T).Line joining (H1, T1) and (H2, T2) is the constant enthalpy line. Choose the correct one from among the alternatives A, B, C and D.
T1-Dew point temp; T2-Dry bulb temp; T3-Wet bulb temp.
T1-Dew point temp; T2-Wet bulb temp; T3-Dry bulb temp.
T1-Wet bulb temp; T2-Dry bulb temp; T3-Dew point temp.
T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.

A

T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.

Philippine Chemical Engineering Licensure Examination Day 2 Separation Processes (14 decks)

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