MASA PASA Flashcards
Mass transfer rate between two fluid phases does not necessarily depend on the __________ of the two phases.
A. chemical properties
In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is
A. 0.5
Fenske equation determines the
C. minimum number of theoretical plates.
The term “cooling range” in a cooling tower refers to the difference in the temperature of
C. hot water entering the tower and the cooled water leaving the tower.
Which of the following is the most suitable for extraction in a system having very low density difference?
B. Centrifugal extractor
Total reflux in a distillation operation requires minimum
B. number of plates
The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is
A. (+)ve
Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the
A. relative volatility is reasonably constant.
When the temperature and humidity of air is low, we usually use __________ draft cooling tower.
A. natural
Pick out the correct statement.
D. all (a), (b) and (c). (A. In case of liquid-liquid extraction, no separation is possible, if the selectivity of the solvent used is unity.) (B. With increase in temperature, the selectivity of the solvent used in solvent extraction decreases.) (C. The selectivity of solvent used in solvent extraction is unity at the plait point.)
__________ columns are used for liquid dispersion in a continuous gas phase.
A. Packed
Overall efficiency of the distillation column is
A. the ratio of number of ideal plates to actual plates.
Which is the controlling factor for a drum drier?
B. Heat transfer
Drying operation under vacuum is carried out to
B. reduce drying temperature.
Air initially at 101. 3 kPa and 40°C and with a relative humidity of 50%, is cooled at constant pressure to 30°C. The cooled air has a
C. higher relative humidity
Separation of two or more components of a liquid solution can not be achieved by
C. absorption
At minimum reflux ratio for a given separation
B. number of plates is infinity.
Relative humidity is the ratio of the
B. partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.
In batch distillation with constant reflux, overhead product composition __________ with time.
B. decreases
Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the __________ of a fibre.
A. electrical resistance
Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the
C. specific heat
To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)
C. increase ‘S’ and decrease ‘G’.
The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = __________
A. 1
Dew point of a gas-vapour mixture
C. decreases with decrease in pressure.
Which of the following plays an important role in problems of simultaneous heat and mass transfer?
A. Lewis number
In case of an absorber, the operating
A. line always lies above the equilibrium curve.
As the reflux ratio in a distillation coloumn is increased from the minimum, the
C. total cost first decreases and then increases.
Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)
B. S1/S2
A plait point is the point on the solubility curve, where the tie line reduces to a point. What is the number of plait point for a ternery system containing twopairs of partially miscible liquids?
A. 0
Make up water is required in a cooling tower to replace the water lost by
D. all (a), (b) and (c) (A. evaporation) (B. drift) (C. blowdown and leakage)
Which of the following quantities need not be fixed before starting the design of a co-current absorber?
B. Flow rate of entering liquid
Mass transfer co-efficient of liquid is
A. affected more by temperature than that for gases.
Absorption accompanied with chemical reaction is exemplified by the absorption of
C. SO2 in alkaline solution.
Which of the following unit operations makes use of Thiele-Geddes equation?
D. Multicomponent distillation.
Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty?
D. Wetted wall column
The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is
C. spray chamber
Chemisorption (chemical adsorption) is
C. an irreversible phenomenon.
The rate of solid-liquid extraction is limited by the
D. all ‘a’, ‘b’ & ‘c’. (A. phase change of the solute as it dissolves in the solvent.) (B. diffusion of the solute through the solvent in the pores to the outside of the particle.) (C.diffusion of the solute from the solution in contact with the particle to the main bulk of the solution. )
Raoult’s law applies to the
D. solvents.
In distillation columns, the number of bubble caps per tray primarily depends upon the
C. allowable gas and liquid velocities.
In distillation, overhead product contains
C. any number of components
With increase in pressure, the relative volatility for a binary system
B. decreases.
Low viscosity absorbent is preferred for reasons of
D. all (a), (b) and (c). (A. rapid absorption rates and good heat transfer characteristics.) (B. improved flooding characteristics.) (C. low pressure drop on pumping.)
Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as
A. K ∝ D
The McCabe Δ L law states that the
C. linear crystal growth rate does not depend on the crystal size.
Bollman extractor
B. is used for extraction of oil from oilseed.
The relation, Sc = Pr = 1, is valid, when the mechanism of __________ ansfer is same.
A. heat and mass
A coalescer in a mixer-settler liquid-liquid extraction coloumn
D. all ‘a’, ‘b’, & ‘c’. (A. comprises of thin bed of substances of extended surface having high porosity.) (B. helps in increasing the bubble size entering the settler.) (C. helps in increasing the settling rate of the bubbles.)
For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will
A. increase
Pick out the correct statement.
A. Ponchan-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.
When the liquid phase and vapour phase of a binary system obeys Raoult’s and Dalton’s law respectively, the relative volatility is the ratio of
A. vapour pressure of component A to that of component B.
The operation involved when the soluble material is largely on the surface of an insoluble solid and is merely washed off by the solvent is called
C. elutriation or elution
In the constant rate period of the rate of drying curve for batch drying,
C. surface evaporation of unbound moisture occurs.
It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%).
C. 71 min
Agitator is provided in a crystalliser for
D. Dall (a), (b) and (c). (A. avoiding deposition on cooler surfaces.) (B. formation of nuclei.) (C.crystal growth.)
__________ diffusion is used for separating the isotopes of methane.
A. Thermal
Ordinary diffusion process is also called __________ diffusion.
C. concentration
Pick out the wrong statement.
C. Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.
Pick out the wrong statement pertaining to the rotary dryer.
C. Rotary dryer is suitable for drying sticky material.
The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives
C. low pressure drop and low hold up.
If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be __________ percent.
B. > 100
Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2. hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is
B. 0.5
Raoult’s law is applicable to the
A. ideal solutions
Weeping in a distillation column
D. results due to very low gas velocity.
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.
Wetted wall tower experiment determines the
C. mass transfer co-efficient.
In McCabe-Thiele method, at infinite reflux ratio
A. the overhead product is minimum.
With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency
A. increases
Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the
A. packing may be crushed due to thermal expansion/contraction of the components of the equipments.
The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is
C. same
Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in __________ tower.
A. wetted wall
Pick out the system with minimum boiling azeotrope at 1 atm.
B. ethyl alcohol-water
Free flowing granular materials can be best dried in a __________ drier.
A. rotary
In case of an ideal solution, the total vapor pressure varies __________ with the composition expressed as mole fraction,
B. linearly
Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the __________ number.
A. Sherwood
If the specific heats of a gas and a vapor are 0.2KJ/Kg.°K and 1.5 KJ/Kg.°K respectively, and the humidity is 0.01; the humid heat in KJ/°Kg. is
D. 0.215
Liquid diffusivity is of the order of __________ cm2 /second.
C. 10-5 to 10-6
The solvent used in liquid extraction should not have high latent heat of vaporisation, because
C. its recovery cost by distillation may be prohibitatively high.
At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid __________ that in dry packed tower.
A. is greater than
Molarity is defined as the number of gm moles of solute per __________ of solvent.
A. liter
The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around
A. 1
Which of the following T-H diagram is valid for dehumidification operation?
A.
An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)
A. less number of trays are required.
The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an __________ law.
A. exponential
Which of the following binary systems is an example of a maximum boiling azeotrope?
A. Water-hydrochloric acid.
(NRe . NSc) is termed in mass transfer operation as the __________ number.
C. Peclet
The binary diffusivity in gases and liquids vary respectively as
A. T^3/2 and T
Pick out the correct statement.
C. In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.
Pick out the correct statement.
B. Electrodylsis is used in the manufacture of NaOH.
Pick out the correct statement.
D. The driving force for mass transfer in a wet solid is its free moisture content.
Very tall packed towers are divided into series of beds to
B. avoid channelling
Moisture contained by a substance in excess of the equilibrium moisture is called the __________ moisture.
B. free
With increase in temperature, the solubility of gases in liquids, at fixed pressure
B. decreases
In most of the vacuum crystalliser, vacuum is generally produced by means of a
C. steam jet ejector with a barometric condenser
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
C. increased reflux ratio
__________ column is the most suitable for achieving the best performance for mass transfer operations involving liquid with dispersed solids.
C. Plate
Deairation (removal of O2) of water is done by
C. ion-exchange
Make up water is supplied during cooling tower operation to compensate for water losses due to
D. all (a), (b)&(c) (A.evaporation ) (B. blowdown) (C. entrainment)
Pick out the wrong statement.
C. Azeotropes obey Raoult’s law at all temperature.
A minimum boiling azeotrope is exemplified by
B. acetone-carbon disulphide
Which of the following solutions will follow Raoult’s law most closely?
A. A solution of benzene, toluene and oxylene.
Use of raschig rings in place of crushed stones as packing in packed beds (other things being same)
C. decreases pressure drop, increases surface area.
The assumption made in Elis method in distillation is that enthalpy concentration lines of vapor and liquid are
C. both parallel and straight
As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches
A. that of normal condensation.
Absorption with chemical reaction’ is involved in the removal of
A. carbon dioxide from gaseous stream using alkaline solution.
The-relative volatility for separation of a non-ideal binary mixture by distillation should be
C. > 1
Pick out the wrong statement:
D. Fenske-Underwood equation is used for calculating theoretical number of plates in a distillation column at normal operating reflux condition.
In paper industry, paper is dried in a __________ dryer.
B. heated cylinder
Pick out the wrong statement.
D. Dehydration of ethyl alcohol is most economically done by molecular distillation at very high vacuum.
Only small amount of evaporation of water produces large cooling effects because of its
A. large latent heat
The most common packing used in industrial operations is __________ rings.
A. raschig
When the feed to a distillation column is a saturated liquid, slope of the feed line is
C. infinity
Leaching of sugar from sugar beets is done by
A. hot water
Absorption factor method is used to calculate the number of ideal stages, when
C. both operating and equilibrium lines are parallel.
Flights in a rotary dryer are provided to
A. lift and shower the solids thus exposing it thoroughly to the drying action of the gas.
If f = moles of vapour present per mole of feed, then the slope of feed line is (Mcabe-Thiele method)
C. -1/f
If the solubilities of different components (in a liquid-liquid extraction system) increase with rise in temperature, then the temperature above which they dissolve completely is known as the critical solution temperature (CST or consolute temperature). If solubilities increase with decrease in temperature, then CST is the temperature below which they dissolve completely. If a binary system has no critical solution temperature, it implies that
D. on heating, a vapor phase will appear ; while on cooling, a solid phase will appear.
The rate of mass transfer is not dependent upon the
D. none of these. (A. degree of dispersion of one fluid in the other.) (B. interfacial surface exposed between the phases.)
At equilibrium the concentration of water in vapour phase (C)in kg/m3 of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C = 0.0667m. To maintain dry conditions in a room of air space 100m3 containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is
C. 0.4
Dry bulb temperature of unsaturated air is more than its __________ temperature.
C. both ‘a’ & ‘b’
For the case of flow of air past a wet bulb thermometer (air water vapour system), the approximate value of h2/ky.Cz is around
C. 1
The reciprocal of stripping factor is termed as
C. absorption factor
Ponchan-Savarit method analyses the fractional equipment based on
C. both enthalpy and material balances.
The binary diffusivity in gases at atmospheric conditions is about
B. 10^-1 cm2/sec
Percentage saturation is __________ the relative saturation.
A. always smaller than
In case of a desorber (stripper), the
B. operating line always lies below the equilibrium curve.
What is the reflux ratio at total reflux?
B. Infinity
Under conditions of flooding in packed tower, the gas pressure drop
D. is maximum
For achieving rapid drying rate in a spray dryer, the diameter of the particles in the feed should be in the range of __________ microns (1 mm = 1000 microns).
B. 10-60
For absorbing a sparingly soluble gas in a liquid
B. liquid side mass transfer co-efficient should be increased.
The change in enthalpy per unit weight of adsorbed gas when adsorbed on gas free or “outgassed” adsorbent to from a definite concentration of adsorbate is called its
A. integral heat of adsorption.
The minimum number of theoretical plates is required for achieving a given separation in distillation column with
B. total reflux
A good solvent used for absorption should not have very high
D. all (a), (b) & (c) (A. viscosity) (B. vapor pressure) (C. freezing point)
In a counter-current liquid extractor
C. only one of the liquids may be pumped at any desired rate.
Which of the following is an undesirable property for an absorbing solvent ?
D. None of these (A. Low vapour pressure) (B. Low velocity) (C. Low freezing point)
The wetted wall tower is used to determine
A. individual mass transfer co-efficient (M.T.C.) in gaseous system.
Weight of 1 m3 of humid air as compared to 1 m3 of dry air, under the same conditions, is
A. less
Positive deviation from Raoult’s law means a mixture whose total pressure is
A. greater than that computed for ideality.
With increase in gas rate, the number of transfer units, NtoG, for a fixed degree of absorption by a fixed amount of solvent
A. increases
Schmidt number is given by
A. μ/ρDAB
Prandtl number for water at 20°C is about
A. 7
Boiling point diagram is
B. affected by pressure.
When acetone is added in a two layer mixture of methyl isobutyl ketone and water at 30°C, the acetone distributes between the two layers and the composition of the layer follows two solubility curves. For this system,
D. all (a), (b) and (c) (A. as the acetone concentration increases, the solubility curves approach each other.) (B. both the phases become identical at a particular common point on both the solubility curves called the plait point.) (C. the distribution curve which is a plot between x (acetone concentration in one phase) and y (acetone concentration in other phase) is analogous to x-y curve used in distillation and absorption terminates on the x = y diagonal at the concentration of the plait point.)
Steam distillation is used to
B. avoid thermal decomposition of a component.
Freundlich equation applies to the adsorption of solute from
A. dilute solutions, over a small concentration range.
For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause __________ plate requirement.
B. marginal decrease in the number of
The apex of an equilateral-triangular coordinate (in ternary liquid system) represents a/an
A. pure component
The diffusivity (D) in a binary gas mixture is related to the pressure (P) as
C. D ∝ 1/P
A slurry is to be dried to produce flaky solid. Which dryer would you recommend?
A. Spray dryer
Which of the following psychrometric processes is followed by water vapour laden unsaturated air, when it is passed through solid or liquid adsorbent?
B. Heating and dehumidification at almost constant wet bulb temperature.
In gas-liquid contact operation, the number of ideal stages, (np picture) . This is true when the stripping factor ‘S’ is
A. S > 1
The cooling effect in a cooling tower can not be increased by
D. none of these. (A. increasing the air velocity over the wet surfaces.) (B. reducing the humidity of entering air.) (C. lowering the barometric pressure.)
The value of NA/(NA + NB) for steady state molecular diffusion of gas ‘A’ through non-diffusing gas ‘B’ is
A. 1
Pick out the wrong statement
D. In actual practice, absorption is an en-dothermic process, while stripping is an exothermic process.
When the mixture to be distilled has a very high boiling point and the product material is heat sensitive, the separation technique to be used is __________ distillation.
B. steam
Large scale drying of wheat is done in a __________ dryer.
B. spouted bed
Azeotropic distillation is employed to separate
A. constant boiling mixture.
The drying time between fixed moisture content within diffusion controlled ‘falling rate period’ is proportional to (assuming that drying occurs from all surfaces of the solid) (where, T = thickness of the solid)
C. T^2
At the boiling point of the liquid at the prevailing pressure, the saturated absolute humidity becomes
C. ∞
Pressure drop through plate tower as compared to that through packed tower, for the same duty will be
B. more
Dimension of mass diffusivity is the same as that of
A. kinematic viscosity
Dorr thickener is an equipment used for
B. sedimentation
Steam distillation is used to separate
B. high boiling substances from nonvolatile impurities.
In distillation where q is defined as the moles of liquid flow in the stripping section per mole of feed introduced, for saturated liquid feed
C. q = 1
Which of the following is an undesirable property in a tower packing?
D. Large weight of liquid retained.
Water entrained by circulating air in cooling towers is termed as
A. drift
A 25 cm x 25 cm x 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m x 1m x 1cm flat sheet of the same material is to be dried from one side only.Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is
A. 1000
With increase in temperature, the rate of leaching increases, because the
A. diffusivity of solute increases.
Humidity chart is useful for the solution of problems concerning condensation, vaporisation and air conditioning. At a given dry bulb temperature, value of humidity obtained from the humidity chart directly, is in terms of __________ humidity.
molal
A. molal
The Kundsen diffusivity is proportional to (where, T = absolute temperature)
A. sqrt(T)
In an absorption coloumn, the flooding velocity for random packing is __________ that for stacked/regular packing.
B. smaller than
The relation among various mass transfer co-efficients (M.T.C) for ideal gases is given by (where, Kc & Km are M.T.C. for equimolar counter diffusion with concentration & mole fraction respectively as the driving force. and, Kp = M.T.C. for diffusion of a gas through a stagnant inert gas with pressure as driving force.)
C. Kc = Kp . RT = Km . RT/p
Leaching of uranium ore and gold ore is done in
B. Pachuka tanks
Blowdown in a cooling tower
A. means discarding a small fraction of circulating water to prevent and limit the concentration of salt and impurities.
Antibiotics are best handled in a
A. Podbielniak extractor.
The fixed cost of a distillation column at minimum reflux ratio is
B. infinite
__________ extractor uses centrifugal force for separating the two phases.
C. Podbielniak
In a binary distillation column, if the feed contains 40 mole % vapour, the q line will have a slope of
C. -1.5
Pick out the wrong statement.
A. Mechanical agitation is required, if the system has low interfacial tension.
Acetic acid will be most economically separated from a dilute solution of acetic acid in water by
A. solvent extraction
Design calculation for multiple component distillation is done by
D. tray to tray calculations.
To get high tray efficiency
A. interfacial surface between liquid and gas phase should be large.
The mass transfer co-efficient for a solid sphere of radius ‘a’ dissolving in a large volume of quiescent liquid, in which D is the diffusivity of solute, is
D. dependent on the Reynolds number
Pick out the wrong statement. Generally for physical adsorption, a gas of
D. none of these. (A. higher molecular weight is adsorbed in preference to a gas of low molecular weight.) (B. high critical temperature is adsorbed in preference to a gas of low critical temperature.) (C. low volatility is adsorbed in preference to a gas of high volatility.)
In most of the mechanically agitated liquid-liquid extractors, baffles or horizontal compartmental plates are provided, which helps in
D. all ‘a’, ‘b’ & ‘c’. (A. reducing the axial mixing.) (B. increasing the rate of extraction.) (C. maintaining the concentration difference between the two phases.)
In a vapor-liquid contacting equipment, the overall gas phase mass transfer co-efficient (M.T.C), KG is related to individual co-efficients (KG and KL) as
B. 1/KG = 1/KG + m/KL
Solvent extraction is the terminology applied to the liquid-liquid extraction, which is preferred for the separation of the components of liquids, when
D. one of the liquid components has very high affinity towards the solvent.
Inside the distillation column, the
A. driving force for the vapour flow is the pressure drop.
Occurrence of ‘case hardening’ during drying of a high moisture solid cake __________ the drying rate.
B. decreases
Which of the following is not a continuous drier?
D. Tray drier
Humidification involves mass transfer between a pure liquid phase and a fixed gas, which is
A. insoluble in the liquid
__________ is the temperature at which a gas-vapor mixture becomes saturated, when cooled at constant total pressure out of contact with a liquid.
A. Dew point
Rate of leaching increases with increasing
A. temperature
An azeotropic mixture is a __________ mixture.
C. constant boiling point
Pick out the wrong statement.
C. 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.
Molecular seives are regenerated by heating to __________ °C.
B. 200-330
In continuous distillation, the internal reflux ratio (Ri) and the external reflux ratio (Re) are related as
. Ri = Re/1+Re
In a counter-current extractor, as the axial mixing increases, the extraction efficiency
B. decreases
Heat sensitive materials like certain pharmaceuticals and food stuffs can be dried in a/an __________ dryer.
C. freeze
In extractive distillation, solvent is
A. added to alter the relative volatility of the mixture.
Radioactive nuclear waste is treated in
C. pulsed column extractor
Large scale drying of sugar is done in a __________ dryer.
C. rotary
__________ temperature is the steady state temperature attained by a small amount of liquid evaporating into a large quantity of unsaturated gas-vapor mixture.
B. Wet bulb
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)
B. T
__________ equation applies to diffusivities in liquids.
A. Gilliland
A packed tower compared to a plate tower for a particular mass transfer operation
A. incurs smaller pressure drop.
Which of the following is the most commonly used leaching solvent in vegetable oil industry?
B. Hexane
In an absorber, HETP does not vary with the
D. none of these (A. flow rate of liquid) (B. flow rate of gas) (C. type and size of packing)
Large quantity of silica gel is normally dried in a __________ dryer.
B. through circulation
For the same system, if the same liquid used in an absorber is decreased, the tower height will
A. increase
Hydrogenation of oil is carried out in a/an __________ in Vanaspati manufacturing plant.
A. agitated vessel
Sides of equilateral-triangular co-ordinates (on which ternary liquid system is plotted) represent
B. a binary mixture.
In distillation column design, the McCabe-Thiele procedure is inadequate and a Ponchan-Savarit procedure is needed, when
D. a total condenser is used.
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
B. gas phase resistance controlled.
As the reflux ratio decreases, the
B. number of plates increases.
Which of the following equipments is not used for gas dispersion?
D. Spray towers
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
C. the fraction vaporised but not the product composition.
The equation, (I33, P12) is for
A. steady state equimolar counter diffusion
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
C. increases
The equation,(I35, P12) is for
B. stready state diffusion for stagnant case.
Which of these columns incurs the lowest pressure drop?
A. Packed column (with stacked packing)
In the desorption of highly soluble gas from the liquid, the main resistance will be in the __________ phase.
B. liquid
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
A. L/G
Which of the following remains constant during evaporative cooling process with recirculated water supply?
C. Wet bulb temperature
For stripping of a gas in a counter current stripper, the operating line
C. can lie above or below the equilibrium curve.
Which of the following same diameter columns gives lowest pressure drop per unit height?
C. Packed column (stacked)
Operating velocity in a packed tower is usually __________ the flooding velocity.
A. half
The Knudsen diffusivity is dependent on the
D. molecular velocity and por radius of the catalyst.
Minimum possible diameter of a packed coloumn is decided mainly by the
A. flooding
Solvent used in extractive distillation
B. forms a low boiling azeotrope.
The cooling effect in a cooling tower can be speeded up by
D. all (a), (b) and (c). (A. increasing the air velocity and area of exposed wet surface.) (B. reducing the barometric pressure.) (C. reducing the humidity of the air.)
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. (I50, P12)
D. T1-Dry bulb temp; T2-Wet bulb temp; T3-Dew point temp.
When both the fluids flow concurrently in an absorber, the slope of the operating line is
A. - ve
The percentage humidity is less than the relative humidity only at __________ percent humidity.
C. both zero and hundred
Back-trapping in a distillation column
B. decreases tray efficiency.
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.
B. more than
Milk is dried usually in a __________ dryer.
B. spray
At a given equilibrium pressure, with increase in temperature, the concentration of adsorbed gas on solid adsorbant
B. decreases
Which of the following adsorbent is used to decolourise yellow glycerine?
D. Activated carbon
Which of the following liquid temperature (T) Vs. vapor-gas mixture enthalpy (H) diagram is valid for humidification operation?
B. (I8, P13)
In a distillation column, with increase in the reflux ratio, the heat removed in the cooler
A. increases.
Pick out the wrong statement.
B. Relative volatility of a binary mixture changes appreciably with the minor change in temperature.
Which of the following is not a unit of mass transfer co-efficient?
D. None of these (A. Moles transferred/(time)(area)(mole fraction)) (B. Moles transferred/(time)(area)(pressure)) (C. Moles transferred/(time)(area)(mass A/mass B))
The falling rate period in the drying of a solid is characterised by
B. increasing temperatures both on the surface and within the solid.
In which of the following unit operations, the selectivity is an important parameter?
B. Solvent extraction
Which of the following is an undesirable characteristic for the solvent used in gas absorption?
D. None of these (A. Low vapor pressure) (B. Low viscosity) (C. High gas solubility)
Which of the following equipments is not used for liquid dispersion?
D. Agitated vessels
Diameter of raschig rings used in packed tower in industry is normally around __________ inches.
A. 2
The diffusion co-efficient in m2 /s. of acetic acid in benzene (liquid in liquid) is
C. 2.09 x 10-9
Pick out the wrong statement.
C. According to film theory for equimolar counter diffusion, the mass transfer coefficient is given by sqrt(DAB)(b)P - 3, Q - 2
In case of non-ideal gases and liquids, the molal diffusivity
C. is independent of pressure.
Condensation of a vapour-gas mixture just begins, when (where, p = partial pressure of the vapour P = vapour pressure of the liquid)
A. p = P
