Mass Transfer (Set 7)

Question 1

In a gas-liquid absorption coloumn, for obtaining the maximum absorption efficiency

Answer 1

both gas as well as liquid streams should be distributed uniformly.

Question 2

Reverse osmosis is also called

Answer 2

ultrafiltration.

Question 3

Which of the following is not a batch drier?

Answer 3

Fluidised bed drier

Question 4

Steam distillation is not recommended to be used, if the

Answer 4

azeotropic mixture is to be separated and the final product is miscible with water.

Question 5

Rayleigh equation applies to ____ distillation.

Answer 5

differential

Question 6

Mass transfer co-efficient ‘K’ according to penetration theory varies with mass dif-fusivity as

Answer 6

D^0.5

Question 7

Most important factor to be considered in the selection of packings for absorbers is the ____ of packing.

Answer 7

porosity

Question 8

____ is the separation technique used for desalination of sea water.

Answer 8

Reverse osmosis

Question 9

The relative saturation of a partially saturated mixture of vapour and gas can be increased by ____ of the mixture.

Answer 9

both (b) and (c)

Question 10

Danckwerts developed the ____ theory.

Answer 10

surface renewal

Question 11

Molecular distillation is

Answer 11

both (b) and (c)

Question 12

Drying of a wet solid under constant drying conditions means the exposure of the wet solid to the air of constant

Answer 12

all (a), (b) & (c)

Question 13

Which of the following provides maximum contact surface for a liquid-vapour system?

Answer 13

Packed tower

Question 14

For experimental determination of mass transfer co-efficient by wetted wall tower, the mass transfer area is

Answer 14

known

Question 15

In stripping section of continuous distillation column, the

Answer 15

liquid is enriched with high boiler.

Question 16

Molality is defined as the number of gm moles of solute per ____ of solvent.

Answer 16

Kg

Question 17

____ is concerned with the adsorption equilibria.

Answer 17

Freundlich equation

Question 18

Which of the following is the correct ternery diagram for liquid-liquid extraction system comprising of one pair partly soluble (e.g. water-benzene-acetic acid in which A-diluent, B - solvent and C - solute)?

Answer 18

https://www.indiabix.com/_files/images/chemical-engineering/mass-transfer/317-498-1.png

Question 19

Fractional solvent extraction

Answer 19

employs two solvents

Question 20

In the layout plan for a vacuum distillation unit, operating at 60 mm Hg, supported by a barometric condenser, the appropriate place for the location of vacuum drum for collecting the distillate will be

Answer 20

at ground level.

Question 21

Raschig ring made of procelain cannot be used for treating concentrated

Answer 21

alkalis

Question 22

H2S present in naphtha reformed gas is removed by absorbing with

Answer 22

ethanolamine

Question 23

During constant rate drying period, vaporisation rate per unit drying surface area

Answer 23

does not change with time,

Question 24

Pick out the wrong statement.

Answer 24

Mass transfer co-efficient does not account for gase-liquid diffusion.

Question 25

In rectifying section of a continuous distillation column, the

Answer 25

vapour is enriched with high boilers.

Question 26

For a fixed number of ideal stages in a distillation column, as the reflux ratio is increased, the difference in composition between the top and bottom product streams

Answer 26

increases

Question 27

According to Chilton-Colburn analogy for mass transfer, NSt.NSc2/3 is equal to

Answer 27

f/2

Question 28

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is

Answer 28

1.24

Question 29

Minimum reflux ratio in a distillation column results in

Answer 29

maximum condenser size.

Question 30

Flooding in a distillation column is detected by a sharp

Answer 30

increase in pressure drop.

Question 31

In extraction, as the temperature increases, the area of hetrogeneity (area covered by binodal curve)

Answer 31

decreases

Question 32

Pick out the wrong statement.

Answer 32

1 Nm3 of dry air is lighter than 1Nm3 of humid air.

Question 33

In case of an unsaturated mixture of gas and vapor, the percentage saturation is ____ its relative saturation.

Answer 33

lower than

Question 34

At constant pressure, with increase of temperature, the dew point will

Answer 34

increase

Question 35

For a single component absorber, the operating line is straight only when plotted in term of ____ units.

Answer 35

mole ratio

Question 36

In case of unsaturated air

Answer 36

both (a) and (b)

Question 37

For a binary mixture with low relative volatility,

Answer 37

an azeotrope may be formed during distillation.

Question 38

Plate efficiency

Answer 38

is a function of the mass transfer between liquid and vapour.

Question 39

Absorption accompanied by heat evolution results in

Answer 39

decrease in equilibrium solubility.

Question 40

Even though bubble cap towers are very effective for humidification operation, they are not used commonly in industries, because of the

Answer 40

high pressure drop of the gas.

Question 41

For a distillation column operating at minimum reflux, the

Answer 41

number of plates required will be maximum.

Question 42

A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids))

Answer 42

MXo ln(Xo/XF)

Question 43

Flash distillation is suitable for the separation of components

Answer 43

having very wide boiling points.

Question 44

In Mcabe-Thiele method, at infinite reflux ratio

Answer 44

both the operating lines coincide with the diagram.

Question 45

Leaching rate is independent of the

Answer 45

none of these

Question 46

Use of packed towers for distillation is generally limited to the

Answer 46

small sizes.

Question 47

Pick out the wrong statement.

Answer 47

Molecular diffusion in solid is much faster than that in liquids.

Question 48

Which of the following decreases during evaporative cooling process with recirculated water supply?

Answer 48

None of these

Question 49

Laboratory determination of the dif-fusivity of vapor is done by ____ method.

Answer 49

Winkel mann's

Question 50

The minimum liquid rate to be used in an absorber corresponds to an operating line

Answer 50

tangential to the equilibrium curve

Question 51

Unsaturated air (with dry and wet bulb temperatures being 35 and 25°C respectively) is passed through water spray chamber maintained at 35°C. The air will be

Answer 51

humidified

Question 52

For absorbing a sparingly soluble gas in a liquid, the

Answer 52

liquid side coefficient should be increased.

Question 53

A natural draft cooling tower is filled with wooden grids, which covers about ____ percent of the tower height.

Answer 53

45580

Question 54

The boiling points of pure components of a binary system ____ with increase in total pressure of the system.

Answer 54

increases

Question 55

The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the

Answer 55

differential heat of adsorption.

Question 56

Penetration theory relates the average mass transfer co-efficient (K) with diffusivity (D) as

Answer 56

K ∝sqrt(D)

Question 57

Desulphurisation of petrol is done in a

Answer 57

rotating disc extractor

Question 58

Chemisorption compared to physical absorption has

Answer 58

increased utilisation of stagnant zones of the liquid phase.

Question 59

Rate of adsorption increases as the

Answer 59

temperature decreases.

Question 60

Pick out the system with maximum boiling azeotrope at 1 atm.

Answer 60

acetone chloroform

Question 61

At 750°K and 1 atm, the approximate value of Schmidt number for air is

Answer 61

0.1

Question 62

Calculation of mass transfer co-efficient is mostly/normally done using ____ theory.

Answer 62

film

Question 63

The velocity, concentration and temperature boundary, for the boundary layer development on a flat plate during connective mass transfer will be same, if

Answer 63

NSc = NPr = NLe

Question 64

For the gas absorption, the height of a transfer unit, based on the gas phase is given by (G: superficial molar gas velocity, L: superficial molar liquid velocity, FG:mass transfer co-efficient, mols/m2 , a: in-terfacial area per unit volume of tower)

Answer 64

G/FG.a

Question 65

Which of the following is used for the concentration of rubber latex?

Answer 65

Agitated film evaporator

Question 66

As the reflux ratio, in a continuous counter-current extraction is increased, the number of stages

Answer 66

decrease

Question 67

In triangular co-ordinates, the ternery composition point falls ____ of the triangle.

Answer 67

inside

Question 68

In a single stage extraction process, 10 kg of pure solvent S (containing no solute A) is mixed with 30 kg of feed F containing A at a mass fraction xf = 0.2. The mixture splits into an extract phase E and a raf-finate phase R containing A at xB = 0.5 and xR = 0.05 respectively. The total mass of the extract phase is (in Kg)

Answer 68

8.89

Question 69

Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and 't' is time)

Answer 69

(4De/πt)^1/2

Question 70

Reboiler is considered as one theoretical plate, because

Answer 70

of the assumption that vapour and liquid leaving the reboiler are in equilibrium.