Mass Transfer Part 2

Question 1

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.

Answer 1

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

Question 2

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

Answer 2

driving force for the vapour flow is the pressure drop.

Question 3

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).

Answer 3

both (a) and (b).

Question 4

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

Answer 4

decreases

Question 5

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

Answer 5

Tray drier

Question 6

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

Answer 6

insoluble in the liquid

Question 7

__________ 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

Answer 7

Dew point

Question 8

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

Answer 8

temperature

Question 9

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

Answer 9

constant boiling point

Question 10

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.

Answer 10

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.

wrong for laminar flow over a plate of length L

Question 11

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

Answer 11

200-330

Question 12

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

Answer 12

Ri = Re/1+Re

Question 13

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

Answer 13

decreases

Question 14

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

Answer 14

freeze

Question 15

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.

Answer 15

added to alter the relative volatility of the mixture.

Question 16

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

Answer 16

pulsed column extractor

Question 17

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

Answer 17

rotary

Question 18

__________ 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

Answer 18

Wet bulb

Question 19

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

Answer 19

T

Question 20

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

Answer 20

Gilliland

Question 21

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.

Answer 21

incurs smaller pressure drop.

Question 22

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

Answer 22

Hexane

hexane solvent vegetable oil leaching

Question 23

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

Answer 23

none of these

HETP does not vary none of these

Question 24

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

Answer 24

through circulation

Question 25

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

Answer 25

increase

Question 26

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

Answer 26

agitated vessel

Question 27

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.

Answer 27

a binary mixture.

Question 28

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.

Answer 28

a total condenser is used.

Question 29

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.

Answer 29

gas phase resistance controlled.

Question 30

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

Answer 30

number of plates increases.

Question 31

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

Answer 31

Spray towers

Question 32

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.

Answer 32

the fraction vaporised but not the product composition.

Question 33

The equation, NA = DAB . Pt / RTZ 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.

Answer 33

steady state equimolar counter diffusion

Question 34

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

Answer 34

increases

Question 35

The equation, NA = DAB . Pt / RTZ . PBM 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.

Answer 35

stready state diffusion for stagnant case.

Question 36

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

Answer 36

Packed column (with stacked packing) ## Footnote lowest pdrop packed stacked

Question 37

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)

Answer 37

liquid

Question 38

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

Answer 38

L/G

Question 39

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

Answer 39

Wet bulb temperature

Question 40

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.

Answer 40

can lie above or below the equilibrium curve.

Question 41

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

Answer 41

Packed column (stacked)

Question 42

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'

Answer 42

both 'a '& 'b'

Question 43

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

Answer 43

both (a) and (b)

Question 44

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

Answer 44

half

Question 45

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.

Answer 45

molecular velocity and por radius of the catalyst.

Question 46

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

Answer 46

flooding

Question 47

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.

Answer 47

forms a low boiling azeotrope.

Question 48

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

Answer 48

both (a) and (b)

Question 49

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).

Answer 49

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

Question 50

The 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. The 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. https://www.indiabix.com/_files/images/chemical-engineering/mass-transfer/335-677-1.png 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.

Answer 50

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

Question 51

When both the fluids flow concurrently in an absorber, the slope of the operating line is - ve (+) ve 1 -1

Answer 51

- ve

Question 52

The percentage humidity is less than the relative humidity only at __________ percent humidity. zero hundred both zero and hundred none of these

Answer 52

both zero and hundred

Question 53

Back-trapping in a distillation column increases tray efficiency. decreases tray efficiency. reduces pressure drop. is desirable, as it provides improved vapour-liquid contact.

Answer 53

decreases tray efficiency. ## Footnote Back-trapping decreases TE

Question 54

Flooding in a vapor-liquid contacting equipment occurs in a tray, when the pressure drop through a tray is __________ the liquid head available in the downcomer. less than more than same as very much less

Answer 54

more than

Question 55

Milk is dried usually in a __________ dryer. freeze spray tray rotary

Answer 55

spray

Question 56

At a given equilibrium pressure, with increase in temperature, the concentration of adsorbed gas on solid adsorbant increases decreases remains unchanged increases exponentially

Answer 56

decreases

Question 57

Which of the following adsorbent is used to decolourise yellow glycerine? Silica gel Alumina Fuller's earth Activated carbon

Answer 57

Activated carbon

Question 58

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

Answer 58

increases.

Question 59

Pick out the wrong statement. Constant pressure distillation can not separate an azeotropic mixture. Relative volatility of a binary mixture changes appreciably with the minor change in temperature. The relative volatility of a binary mixture at azeotropic composition is unity. Flash distillation is practised on wide spread scale in petroleum refinery.

Answer 59

Relative volatility of a binary mixture changes appreciably with the minor change in temperature.

Question 60

Which of the following is not a unit of mass transfer co-efficient? Moles transferred/(time)(area)(mole fraction) Moles transferred/(time)(area)(pressure) Moles transferred/(time)(area)(mass A/mass B) None of these

Answer 60

None of these

Question 61

The falling rate period in the drying of a solid is characterised by increase in rate of drying. increasing temperatures both on the surface and within the solid. decreasing temperatures. none of these.

Answer 61

increasing temperatures both on the surface and within the solid.

Question 62

In which of the following unit operations, the selectivity is an important parameter? Distillation Solvent extraction Absorption None of these

Answer 62

Solvent extraction

Question 63

Which of the following is an undesirable characteristic for the solvent used in gas absorption? Low vapor pressure Low viscosity High gas solubility None of these

Answer 63

None of these

Question 64

Which of the following equipments is not used for liquid dispersion? Wetted wall towers Packed towers Venturi scrubers Agitated vessels

Answer 64

Agitated vessels

Question 65

Diameter of raschig rings used in packed tower in industry is normally around __________ inches. 2 8 12 18

Answer 65

2

Question 66

The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is 2.09 x 10-4 2.09 x 10-5 2.09 x 10-9 2.09 x 10-12

Answer 66

2.09 x 10-9 ## Footnote AAB9 acetic acid in benzene 10^-9

Question 67

Pick out the wrong statement. The Reynolds analogy for mass transfer is given by Lewis relation and is applicable, when Schmidt number is one. Sherwood number for flow in pipes can be expressed as the ratio of the concentration gradient at wall to the overall concentration difference. According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by sqrt(DAB)(b)P - 3, Q - 2 The z-component of the total mass flux of a component A in binary mixture of A and B is given by - Dab'.dCA/dz.

Answer 67

According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by sqrt(DAB)(b)P - 3, Q - 2 ## Footnote wrong according to film theory sqrt(DAB)...

Question 68

In case of non-ideal gases and liquids, the molal diffusivity varies inversely as the pressure. varies directly as the pressure. is independent of pressure. is equal to the volumetric diffusivity.

Answer 68

is independent of pressure.

Question 69

Condensation of a vapour-gas mixture just begins, when (where, p = partial pressure of the vapour P = vapour pressure of the liquid) p = P p > > P p < P p < < P

Answer 69

p = P

Question 70

__________ number indicates the ratio of the rates of the heat and mass transfer incase of a cooling tower. Sherwood Stanton Lewis Peclet

Answer 70

Lewis

Question 71

The expression, y(1 - x)/x(1 - y) is for absorption factor relative volatility selectivity Murphree efficiency

Answer 71

relative volatility

Question 72

In physical terms, Schmidt number means thermal diffusivity/mass diffusivity. thermal diffusivity/momentum diffusivity. momentum diffusivity/mass diffusivity. mass diffusivity/thermal diffusivity.

Answer 72

momentum diffusivity/mass diffusivity.

Question 73

In case of liquids, the binary diffusivity is proportional to (where, T = temperature) T √T T^2 1/T

Answer 73

T ## Footnote binarydiffusivity T

Question 74

The diffusivity, DAB (for component A diffusing in B) is equal to the diffusivity DBA (for component B diffusing in A) for a binary mixture of Newtonion liquids non-Newtonion liquids ideal gases real gases

Answer 74

ideal gases

Question 75

Mass transfer co-efficient is directly proportional to DAB0.5, according to __________ theory. penetration surface renewal film none of these

Answer 75

penetration

Question 76

Sand is dried in foundaries in a___drier. rotary fluidised bed vacuum spray

Answer 76

fluidised bed

Question 77

Which of the following employs an accessory known as 'drift eliminator'? Multiple effect evaporator. Mechanical draft cooling tower. Rotary dryer. Rotating disc contactor.

Answer 77

Mechanical draft cooling tower.

Question 78

Pick out the correct statement. Higher hold up of the solid in the rotary dryer results in better exposure of the solids to the gas. The 'Hatta number' is important in problems involving gas absorption without chemical reaction. For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion. Total reflux in case of distillation operation requires infinite number of plates for a binary system separation.

Answer 78

For a non-reacting binary mixture of ideal gases, the partial pressure distribution of both components is linear in the case of steady state equimolal counter-diffusion.

Question 79

Pick out the correct statement. For identical gas flow rates, less pressure drop occurs through a plate tower than through a packed tower. Plate column can handle greater liquid loads without flooding than packed column, but the liquid hold up is more in the case of plate column. For the same duty, plate columns weigh less than packed columns. all (a), (b) and (c).

Answer 79

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

Question 80

Humid volume is the total volume in m3 of 1 kg of vapour laden gas at 1 atm. and room temperature. gas plus its accompanying vapour at 1 atm. and room temperature. gas plus its accompanying vapour at 1 atm. and gas temperature. vapour laden gas at 1 atm. and gas temperature.

Answer 80

gas plus its accompanying vapour at 1 atm. and gas temperature. ## Footnote humid volume gas plus gas temperature

Question 81

Diameter to height ratio for a rashig ring is 1 0.5 2 8

Answer 81

1 ## Footnote 1 rashig

Question 82

The equipment used in the extraction of highly corrosive radio active liquids is pulse column spray column mixer settler baffle tower

Answer 82

pulse column

Question 83

Advantage of continuous drying over batch drying is that the drying cost per unit weight of dried product is less. product with more uniform moisture content is produced. equipment size required is smaller. all 'a', 'b' & 'c'

Answer 83

all 'a', 'b' & 'c'

Question 84

With increase in temperature, the rate of extraction in leaching (solid-liquid extraction system) increases decreases remains unaffected increases linearly

Answer 84

increases

Question 85

In a packed bed absorption column, the channelling will be noted by the increase in flow rate. sharp drop in pressure drop. sharp rise in pressure drop. none of these.

Answer 85

sharp drop in pressure drop.

Question 86

Gaseous diffusivity at atmospheric pressure is of the order of __________ cm2/second. 1 1 to 5 5 to 10 > 10

Answer 86

1

Question 87

In liquid-liquid extraction, the number of phases at plait point is 1 2 3 4

Answer 87

1

Question 88

In a liquid-liquid extraction, 10 kg of a solution containing 2 kg of solute C and 8 kg of solvent A is brought into contact with 10 kg of solvent B. Solvent A and B are completely immiscible in each other whereas solute C is soluble in both the solvents. The extraction process attains equilibrium. The equilibrium relationship between the two phases is Y* = 0.9X, where Y* is the kg of C/kg of B and X is kg of C/kg of A. Choose the correct answer. The entire amount of C is transferred to solvent B. Less than 2 kg but more than 1 kg of C is transferred to solvent B. Less than 1 kg of C is transferred to B. No amount of C is tranferred to B.

Answer 88

The entire amount of C is transferred to solvent B.

Question 89

The surface renewal frequency in Danckwerts' model of mass transfer is given by (KL: mass transfer co-efficient) sqrt(KL2.DA) KL2.DA KL2/DA KL/DA2

Answer 89

sqrt(KL2.DA)

Question 90

If Rm is the minimum reflux ratio, the optimum reflux ratio may be around __________ Rm. 1.2 to 1.5 2.5 to 3 3 to 4 5

Answer 90

1.2 to 1.5

Question 91

During dehumidification of unsaturated air wet bulb temperature & partial pressure of vapor are not constant. However, during evaporative cooling process with recirculated water supply, the __________ remains constant. wet bulb temperature partial pressure of water vapor relative humidity none of these

Answer 91

wet bulb temperature

Question 92

In case of absorption, both the operating and equilibrium lines will be straight for isothermal operation. dilute solutions. dilute solutions and isothermal operation. none of these.

Answer 92

dilute solutions and isothermal operation.

Question 93

Mass transfer co-efficient varies as DAB0.5, according to the __________ theory. film surface renewal penetration none of these

Answer 93

surface renewal

Question 94

For an absorber, both equilibrium and operating line will be straight for concentrated solution and non-isothermal operation. dilute solution and non-isothermal operation. dilute solution and isothermal operation. concentrated solution and isothermal operation.

Answer 94

dilute solution and isothermal operation.

Question 95

A distillation column separates 10000 kg/hr of a benzene-toluene mixture as shown in the figure below: https://www.indiabix.com/_files/images/chemical-engineering/mass-transfer/335-680-1.png In the figure xF, xD and xW represent the weight fraction of benzene in the feed, distillate and residue respectively. The reflux ratio is 0.5 0.6 1 2

Answer 95

0.6

Question 96

Unsaturated air (with dry bulb and wet bulb temperatures being 45 C and 25 C respectively) is passed through a water spray chamber maintained at 23 C. The air will be cooled and humidified with wet bulb temperature decreasing. humidified at constant wet bulb temperature. dehumidified. none of these

Answer 96

humidified with wet bulb temperature decreasing.

Question 97

Humid volume, at a given temperature is a/an __________ function of humidity. inverse exponential linear logarithmic

Answer 97

linear

Question 98

The Schmidt number which is defined as, u/rho D, is the ratio of the momentum diffusivity to the mass diffusivity. thermal diffusivity to the mass diffusivity. momentum diffusivity to the thermal diffusivity. none of these.

Answer 98

momentum diffusivity to the mass diffusivity.

Question 99

If f is defined as above, then which of the following applies to a feed at dew point ? f = 1 f < 1 f > 1 0 < f < 1

Answer 99

f = 1

Question 100

Perforated plate towers are unique for solvent extraction because, they provide higher contact area. better contact of the phase. repeated coalescence & redispersion of the drop phase. none of these.

Answer 100

repeated coalescence & redispersion of the drop phase.

Question 101

In case of absorption & stripping, the interface of the liquid & gas phases are present in equilibrium, when the diffusional resistance of __________ is zero. interface gas phase liquid phase all 'a', 'b' & 'c'

Answer 101

interface

Question 102

Pick out the wrong statement pertaining to the analogy between equations of heat and mass transfer operations. Sherwood number in mass transfer is analogous to Nusselt number in heat transfer. Prandtl number in heat transfer is analogous to Schmidt number in mass transfer. Reynolds number in mass transfer is analogous to Grashoff number in heat transfer. Reynolds number remains the same in both heat and mass transfer.

Answer 102

Reynolds number in mass transfer is analogous to Grashoff number in heat transfer.

Question 103

The slope of the operating line for a single component co-current absorber when plotted in terms of mole ratio units is 0 infinite (-) ve (+) ve

Answer 103

(-) ve

Question 104

The individual mass transfer co-efficients (moles/m2 . s) for absorption of a solute from a gas mixture into a liquid solvent are, KL = 4.5 and KG = 1.5. The slope of the equilibrium line is 3. Which of the following resistance (s) is (are) controlling? liquid side gas side interfacial both liquid and gas side

Answer 104

gas side

Question 105

Pore size of the molecular seive 5A is __________ mm. 5 0.5 0.05 50

Answer 105

0.5

Question 106

Swenson-Walker crystalliser is a __________ unit continuous batch semi-batch cooling (adiabatic)-cum-evaporation

Answer 106

continuous ## Footnote SWC Swenson-Waler continuous

Question 107

According to the Fenske equation, what will be the minimum number of plates required in a distillation column to separate an equimolar binary mixture of components A and B into an overhead fraction containing 99 mol% A and a bottom fraction containing 98 mol% B ? Assume that relative volatility (αAB = 2) does not change appreciably in the coloumn. 5 9 12 28

Answer 107

12 ## Footnote ln{[0.99/(1-0.99)] * [(1-0.02)/0.02]} / ln(2) = 12.25

Question 108

Absorption (liquid-gas system) with evolution of heat as compared to isothermal absorption results in decreased solute solubility. large minimum liquid to gas (L/G) ratio. large number of trays. all (a), (b) and (c).

Answer 108

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

Question 109

With increase in temperature, the mutual solubility of two liquids increases decreases remains unchanged decreases exponentially

Answer 109

increases

Question 110

Pick out the wrong statement. In solvent extraction, the distribution co-efficient should be as large as possible for solvent economy. With increase in pressure, the solubility of gases in solvent increases at a fixed temperature. Decrease in Murphree plate efficiency is an indication of entrainment in distillation column. The capacity of a distillation coloumn is maximum at total reflux.

Answer 110

The capacity of a distillation coloumn is maximum at total reflux. ## Footnote wrong capacity maximum at total reflux

Question 111

The relative volatility of a binary mixture at the azeotropic composition is 1 > 1 0 infinite

Answer 111

1

Question 112

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 only vapor phase follows Raoult's law. only liquid phase obeys Dalton's law. liquid phase obeys Dalton's law and vapor phase obeys Raoult's law. Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.

Answer 112

Vapor phase obeys Dalton's law and liquid phase obeys Raoult's law.

Question 113

Bound moisture is that liquid which exerts an equilibrium vapor pressure __________ that of the pure liquid at the given temperature. less than more than equal to either (o) or (b); depends on the solid

Answer 113

less than

Question 114

Lewis number (Le) is Sc / Pr Pr x St Sh x Pr St x Sh

Answer 114

Sc / Pr

Question 115

Which of the following is not a continuous leaching equipment? Pachuka tank Kennedy extractor Bollman extractor Hydrocyclones

Answer 115

Pachuka tank

Question 116

__________ extractor is used for the concentration of radioactive nuclear waste. Pulsed column Sieve plate Mixer-settler Ballman

Answer 116

Pulsed column

Question 117

Moisture content of a substance when at equilibrium with a given partial pressure of the vapour is called the __________ moisture. free unbound equilibrium bound

Answer 117

equilibrium

Question 118

All moisture in a non-hygroscopic material is the __________ moisture. free equilibrium unbound bound

Answer 118

unbound

Question 119

Pick out the correct relationship. (where, Ri = internal reflux ratio Ro = external reflux ratio.) (1 + Ro) = Ro/Ri (1 - Ro) = Ro/Ri (1 + Ri) = Ro/Ri (1 - Ri) = Ro/Ri

Answer 119

(1 + Ro) = Ro/Ri

Question 120

Separation of __________ employs gaseous diffusion process. N2 and O2 from air isotopes of uranium isotopes of helium SO2 and air

Answer 120

isotopes of uranium

Question 121

For water-ethanol system, the minimum reflux ratio is computed from the slope of the upper operating line that is tangent to the equilibrium curve. is computed from the intercept of the operating line. cannot be computed. is the optimum reflux ratio.

Answer 121

is computed from the slope of the upper operating line that is tangent to the equilibrium curve.

Question 122

The interfacial area per unit volume of dispersion, in a gas-liquid contactor, for fractional hold up of gas = 0.1 and gas bubble diameter = 0.5 mm is given by (in m2/m3) 500 1200 900 800

Answer 122

500

Question 123

Though, theoretically the adsorption & desorption isotherms is expected to coincide but sometimes at least a part of the isotherms does not coincide and this phenomenon is known as adsorption hysterisis. In such cases, the desorption equilibrium pressure is __________ that obtained for adsorption. lower than higher than same as either same or higher than

Answer 123

lower than ## Footnote adsorption hysterisis lower than

Question 124

Experimental determination of __________ is done by wetted wall column method. diffusion co-efficient mass transfer co-efficient NTU none of these

Answer 124

mass transfer co-efficient ## Footnote wetted wall mass transfer co efficient

Question 125

Pick out the wrong statement: Absorption factor is constant, when the equilibrium and operating lines are straight. In case of a stripper, the equilibrium curve is always below the operating line. In case of an absorber, the operating line is always above the equilibrium curve. In the absorption of low solubility gases, the liquid film is the controlling resistance.

Answer 125

In case of a stripper, the equilibrium curve is always below the operating line.

Question 126

In liquid extraction, if the selectivity is unity, then separation of the constituents is the most effective. no separation will occur. amount of solvent required will be minimum. solvent flow rate should be very low.

Answer 126

no separation will occur.

Question 127

Paper industry employs __________ driers. cylinder rotary spray fluidised bed

Answer 127

cylinder

Question 128

Which of the following has the same dimension as mass diffusivity? Momentum flux Kinematic viscosity Thermal diffusivity Both (b) and (c)

Answer 128

Both (b) and (c)

Question 129

Pick out the wrong statement pertaining to the cooling towers. In case of induced draft cooling tower, the fan is placed at the top of the tower. Effectiveness of forced draft cooling tower is reduced by the recirculation of the humid and hot discharged air. A natural draft cooling tower is recommended to be used, when the air humidity is low and air temperature is also low. Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

Answer 129

Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature.

Question 130

Experiments were conducted to determine the flux of a species A in a stagnant medium across a gas-liquid interface. The overall mass transfer co-efficient based on the liquid side for dilute systems for the above was estimated to be 4 x 10-3 kg mole/m2.s. The equilibrium data for the system is given as y = 2x. The flux across the interface (in kg mole/m2 .s) for bulk concentrations of A in gas phase and liquid phase as y = 0.4 and x = 0.01 respectively is 5.6 x 10-4 8.5 x 10-4 5.6 x 10-3 8.5 x 10-3

Answer 130

8.5 x 10-4

Question 131

Leaching of coarse solid lumps is also termed as decoction dissolution percolation agitation and settling

Answer 131

percolation

Question 132

The main reason for dividing a tall packed tower into series of small towers is to minimise the overall pressure drop. avoid flooding. reduce liquid hold up. avoid channeling.

Answer 132

avoid channeling.

Question 133

Co-current absorbers are usually used when the gas to be dissolved in the liquid is sparingly soluble highly soluble a pure substance a mixture

Answer 133

a pure substance ## Footnote co-current pure substance

Question 134

At what percentage (by volume) of alcohol composition, it forms an azeotrope with water? 90 91.5 95 99

Answer 134

95

Question 135

Measurement of the interfacial area of mass transfer is achieved easily & accurately in case of a __________ coloumn. spray packed bubble cap plate wetted wall

Answer 135

wetted wall

Question 136

With the lowering of equiliDrium pressure, at a given temperature, the amount of ad-sorbate on the adsorbent increases. decreases. remains same. either (a) or (b), depends on the system.

Answer 136

decreases.

Question 137

Mass transfer co-efficient is defined as Flux = Co-efficient/concentration difference. Co-efficient = Flux/concentration difference. Flux=concentration difference/co-effi-cient. none of these.

Answer 137

Co-efficient = Flux/concentration difference.

Question 138

When an unsaturated air-water mixture is heated at constant pressure, then the partial pressure of water vapour increases. the specific humidity decreases. The relative humidity increases. the relative humidity decreases.

Answer 138

the relative humidity decreases.

Question 139

During sensible cooling process relative humidity decreases relative humidity increases wet bulb temperature decreases both (b) and (c)

Answer 139

both (b) and (c)

Question 140

At a fixed pressure, the humidity depends upon the partial pressure of vapor in the mixture. Humidity of a vapour free gas is __________ percent. 100 0 50 between 0 and 100

Answer 140

0

Question 141

In case of physical adsorption, the difference between heat of adsorption and heat of normal condensation is equal to the heat of formation of surface compound. equal to the heat of wetting. zero. called integral heat of adsorption.

Answer 141

equal to the heat of wetting.

Question 142

Pick out the wrong statement: Change in barometric pressure does not affect the relative humidity. In case of a packed tower, the operating velocity is about half of the flooding velocity, generally. Elution' means the desorption of the adsorbed solute by a solvent. The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

Answer 142

The equilibrium moisture content of the solid can be reduced by increasing the absolute humidity.

Question 143

The value of L/mG ratio for economical absorption operation ranges from 0.5 to 0.8 0.8 to 1.2 1.25 to 2.0 2.5 to 3.5

Answer 143

1.25 to 2.0

Question 144

Large scale usage of flash distillation is practised in soap manufacturing ammonia synthesis plant polymerisation industry petroleum refinning

Answer 144

petroleum refinning

Question 145

High pressure at the bottom of a distillation tower handling heat sensitive materials results in thermal decomposition of bottoms. increased relative volatility. erosion of the tower. very efficient operation.

Answer 145

thermal decomposition of bottoms.

Question 146

Alcohol is dehydrated using __________ distillation. extractive azeotropic steam molecular

Answer 146

azeotropic

Question 147

Separation of two volatile liquids by distillation makes use of their selectivity relative volatility solubility density difference

Answer 147

relative volatility

Question 148

Which of the following increases during evaporative cooling process with recirculated water supply? Wet bulb temperature Relative humidity Partial pressure of vapour Both (b) and (c)

Answer 148

Both (b) and (c)

Question 149

Dried finished product sampled from various parts of a __________ dryer exhibits non-uniformity in the moisture content. rotary tray freeze none of these

Answer 149

tray

Question 150

__________ is used as an 'entrainer' for the separation of acetic acid-water mixture by distillation. Furfural Benzol Butyl acetate Hexane

Answer 150

Butyl acetate

Question 151

Rotary dryers cannot handle __________ materials. free flowing dry sticky granular

Answer 151

sticky

Question 152

Pick out the correct statement. Diffusivity decreases with increase in temperature. Diffusivity increases with increase in molecular weight. Diffusivity increases with the size of the individual molecule. none of these.

Answer 152

none of these.

Question 153

An example of elution is separation of uranium oxide from its ore by H2SO4 in a Pachuca tank. separation of sugar from sugar beet by hot water. dissolution of tannin out of tree barks by water. recovery of vegetable oils from seeds.

Answer 153

separation of uranium oxide from its ore by H2SO4 in a Pachuca tank.

Question 154

The operating line for an absorber is curved, when plotted in terms of mole fractions mole ratios partial pressure mass fractions

Answer 154

partial pressure

Question 155

Relative volatility does not change appreciably with the change in temperature vapour pressure of either component total pressure none of these

Answer 155

temperature

Question 156

Boiling point diagram is not affected by the ambient pressure humidity temperature both (b) and (c)

Answer 156

both (b) and (c)

Question 157

The dew point of a saturated gas phase equals the __________ temperature. gas room wet bulb none of these

Answer 157

gas ## Footnote dew point - sat gas - gas temp

Question 158

A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process? Flow rate of inlet air Relative humidity of outlet air Humidity of inlet air Temperature of the solid

Answer 158

Temperature of the solid

Question 159

In case of liquid-liquid binary diffusion, diffusivity of one constituent into another is not dependent on the temperature and pressure concentration nature of the constituents none of these

Answer 159

none of these

Question 160

For continuous drying of grannular or crystalline material, the dryer used is the __________ dryer. tunnel tray rotary none of these

Answer 160

rotary

Question 161

When adsorption hysteresis is observed, the desorption equilibrium pressure is __________ that obtained by adsorption. always lower than always higher than same as dependent on the system; can be either lower or higher than

Answer 161

always lower than

Question 162

Moisture in a substance exerting an equilibrium vapour pressure less than that of pure liquid at the same temperature is called the __________ moisture. bound unbound critical none of these

Answer 162

bound

Question 163

For a binary mixture with low relative volatility, continuous rectification to get pure products will require low reflux ratio less number of trays small cross-section column high reflux ratio

Answer 163

high reflux ratio

Question 164

The efficiency of a plate column will be maximum, when the flow is ideal __________ the plate. across above both (a) & (b) neither (a) nor (b)

Answer 164

both (a) & (b)

Question 165

Heat load in a cooling tower means the amount of heat thrown away (KCal/hr.) by the cooling tower. is equal to the number of kg, of water circulated times the cooling range. both (a) & (b). neither (a) nor (b).

Answer 165

both (a) & (b).

Question 166

In case of absorption with exothermic reaction, for fluids having Pr = Sc; percentage change in heat and mass transfer flux will be the same for a given change in the degree of turbulence. Pr = Sc = 1; total mass, momentum and thermal diffusivity will be the same. both (a) and (b) Pr = Sc ; there won't be any change in heat and mass transfer flux with changes in degree of turbulence.

Answer 166

both (a) and (b)

Question 167

Detergent solution is dried to a powder in a spray dryer spouted bed dryer tunnel dryer pan open to atmosphere

Answer 167

spray dryer

Question 168

Which of the following mixtures does not form an azeotrope at atmosheric pressure? Water-alcohol Methyl alcohol-acetone Butyl acetate-water None of these

Answer 168

None of these

Question 169

During bottling of cold drinks (e.g. Pepsi), the main resistance to mass transfer for the absorption of carbon dioxide in water lies in the gas film liquid film liquid-gas interface none of these

Answer 169

liquid film

Question 170

The overall mass transfer co-efficient for the absorption of SO2 in air with dilute NaOH solution can be increased substantially by increasing the gas film co-efficient. increasing the liquid film co-efficient. increasing the total pressure. decreasing the total pressure.

Answer 170

increasing the gas film co-efficient.

Question 171

Flooding results in high tray efficiency low tray efficiency high gas velocity good contact between the fluids

Answer 171

low tray efficiency

Question 172

For the air water system under ambient conditions, the adiabatic saturation temperature and the wet bulb temperature are nearly equal, because water has a high latent heat of evaporation. Lewis number is close to unity. they are always equal under all circumstances. solubility of the components of air in water is very small.

Answer 172

water has a high latent heat of evaporation.

Question 173

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

Answer 173

driving force for the vapor flow is the pressure drop, as the pressure decreases gradually from the bottom to the top of the column.

Question 174

In a forced draft cooling tower, water is cooled from 95 to 80 F by exposure to air with a wet bulb temperature of 70 F. In this case, the range is 15 F. approach is 10 F. both (a) & (b). neither (a) nor (b).

Answer 174

both (a) & (b).

Question 175

The diffusivity (D) in a binary gas mixture is related to the temperature (T) as D is proportional to T D is proportional to T^0.5 D is proportional to T^1.5 D is proportional to T^2

Answer 175

D is proportional to T^1.5

Question 176

For which of the following unit operations, Lewis number is of significance? Adsorption Binary distillation Gas absorption Humidification

Answer 176

Humidification

Question 177

Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches. 5 30 60 100

Answer 177

30

Question 178

If a1 and a2 are the relative volatilities when the pressure in the distillation column is 1 and 2 atm respectively. Pick out the correct statement. a1 = a2 a1 = 2a2 a1 = 0.5 a2 none of these

Answer 178

none of these ## Footnote a1 a2 none of these

Question 179

The dimension of diffusivity is same as that of the density molal concentration kinematic viscosity velocity head

Answer 179

kinematic viscosity

Question 180

The temperature to which a vapour gas mixture must be cooled (at varying humidity) to become saturated is called the __________ temperature. dew point wet bulb dry bulb none of these

Answer 180

none of these

Question 181

Entrainer used in azeotropic distillation should form a low boiling azeotrope with one of the constituents of the mixture. form a new azeotrope of low relative volatility with one of the constituents of the mixture. have high latent heat of vaporisation. have high viscosity to provide high tray efficiency.

Answer 181

form a low boiling azeotrope with one of the constituents of the mixture.

Question 182

In case of steam distillation, the steam leaving the liquid is not completely saturated with distillate vapour, because temperature is less. total pressure is less. mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition. saturated steam is used for steam distillation.

Answer 182

mixing of steam with the material being vaporised is not so intimate as to result in equilibrium condition.

Question 183

Pick out the wrong statement. The operating line always lies above the equilibrium solubility curve in case of a single component absorber. The operating line always lies below the equilibrium solubility curve in case of a single component stripper. The operating pressure in solvent extraction system should be below vapor pressures of all components. The solubility of a particular gas in ideal solution in any solvent is always the same.

Answer 183

The operating pressure in solvent extraction system should be below vapor pressures of all components.

Question 184

Leaching of coffee from coffee beans is done by hot water hexane lime water dilute H2SO4 (hot)

Answer 184

hot water

Question 185

For contacting a highly soluble gas with a liquid bubble the gas through liquid. spray the liquid on gas stream. either (a) or (b) would suffice. none of these.

Answer 185

bubble the gas through liquid.

Question 186

During drying operation, it is easier to remove the __________ moisture. equilibrium critical unbound bound

Answer 186

unbound

Question 187

With increase in solvent rate, the number of transfer units, NtoG, for a fixed degree of absorption from a fixed amount of gas increases decreases decreases linearly remains unaffected

Answer 187

decreases

Question 188

Ion exchange process is similar to absorption adsorption extraction leaching

Answer 188

adsorption

Question 189

A distillation column with N plates is being operated under normal conditions. At some point of time, the operation is shifted to total reflux condition (i.e., no product and residue are being withdrawn and feed to the column is stopped). At the new steady state, composition of vapors and that of liquid do not vary throughout the column. reboiler load and condenser load are minimum. the top and bottom compositions are unchanged with and without total reflux. the top and bottom compositions correspond to the maximum enrichment available.

Answer 189

the top and bottom compositions correspond to the maximum enrichment available.

Question 190

Dryer widely used in a textile industry is __________ dryer. festoon cylinder conveyor tunnel

Answer 190

conveyor

Question 191

Solvent used in extractive distillation changes the relative volatility of the original components. should be of high volatility. should form azeotropes with the original components. all (a), (b) and (c)

Answer 191

changes the relative volatility of the original components.

Question 192

Air at a particular humidity is heated in a furnace. The new dew point decreases increases depends on the extent of heating remain unchanged

Answer 192

increases

Question 193

In a packed tower, the value of HETP equals HTUOG, when the equilibrium and the operating lines are (where, HETP = height equivalant to a theoretical plate HTUOG = overall gas phase height of a transfer unit) straight parallel both (a) & (b) neither (a) nor (b)

Answer 193

both (a) & (b)

Question 194

The vapour pressure exerted by the moisture contained in a wet solid depends upon the nature of the moisture. temperature. nature of the solid. all (a), (b) and (c).

Answer 194

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

Question 195

The absorption factor is defined as (where, L = liquid flow rate, G = gas flow rate and, m = slope of the equilibrium line) L/mG G/mL mL/G LG/m

Answer 195

L/mG

Question 196

Smoke is an example of solid dispersed in liquid solid dispersed in gas liquid dispersed in gas gas dispersed in liquid

Answer 196

solid dispersed in gas

Question 197

Which of the following adsorbant is used in the refinning of sugar? Bone charcoal Wood charcoal Silica gel Activated clay

Answer 197

Bone charcoal ## Footnote bone sugar

Question 198

Stacked packing compared to dumped packing provides poorer contact between the fluids. gives lower pressure drop. both (a) and (b). gives higher pressure drop.

Answer 198

both (a) and (b).

Question 199

In McCabe-Thiele method of theoretical plate calculation for a distillation column, the operating lines of stripping and rectifying sections coincide with the diagonal at __________ reflux. total minimum operating maximum permissible

Answer 199

total