SEPARATION PROCESSES Flashcards
Which of the following operations does not involve leaching?
a. Dissolving gold from ores.
b. Dissolving pharmaceutical products from bark or roots.
c. Dissolving sugar from the cells of the beet.
d. Removing nicotine from its water solution by kerosene.
D. Removing nicotine from its water solution by kerosene
Tea percolation employs
a. solvent extraction
b. leaching
c. absorption
d. adsorption
B. leaching
Neem oil is a traditional plant product which possesses
spermicidal properties. A group of students working on their
investigatory project wanted to test how effective the said oil was
as contraceptive by using it as a component for contraceptives.
The students were able to gather 5 kg of Neem Tree Seeds that
contains 30% of soluble oil and 70% inert solids and they decided
to use 5 kg of pure hexane to extract the oil. What percentage of
oil will they be able to recover given that the ratio of the liquid to
solid components in the underflow is 0.5? Assume ideal
leaching.
a. 88%
b. 93%
c. 73%
d. 65%
c. 73%
Which of the following is the most commonly used leaching
solvent in vegetable oil industry?
a. phenol
b. hexane
c. furfural
d. liquid SO2
B. hexane
Leaching of sugar from sugar beets is done using
a. hot water
b. hexane
c. dilute H2SO4
d. lime water
A. hot water
In a determination of the solution retention data, the mass fraction
of the solute in the extract was determined to be 0.6. The
corresponding underflow analysis showed a retention of 0.6 kg
solvent per kg of the inert solid. The mass fraction of solute in the
underflow is most likely
a. 0.60
b. 0.36
c. 0.47
d. 0.27
B. 0.36
In a salt recovery plant, rock salt is being leached to produce
industrial salt in a continuous counter current system consisting
of two ideal stages using water as leaching medium. the average
composition of the rock salt is: inerts = 70%, soluble salts = 25%,
moisture = 5%, all percentage by weight. The underflow from
each stage contains 0.3 kg of solution per kg of inerts. The plant
leaches 50 MT of rock salt per day using 50 MT of water.
- The quantity of soluble salts recovered in MT/day is
a. 12.1
b. 14
c. 13.1
d. 11.2 - The composition of salt in weight percent in the final underflow is
a. 0.88%
b. 0.78%
c. 0.98%
d. 0.68%
- A. 12.1
- A. 0.88%
Rate of leaching increases with increasing
a. temperature
b. pressure
c. viscosity of solvent
d. size of the solid
A. temperature
In a counter-current extractor, as the axial mixing increases, the
extraction efficiency
a. increases
b. decreases
c. remains unchanged
d. depends on the pressure of the system
B. decreases
0.4 kg/s of dry sea-shore sand, containing 1 per cent by mass of
salt, is to be washed with 0.4 kg/s of fresh water running counter
currently to the sand through two classifiers in series. It may be
assumed that perfect mixing of the sand and water occurs in each
classifier and that the sand discharged from each classifier
contains one part of water for every two of sand by mass.
- If the washed sand is dried in a kiln dryer, what percentage of salt
will it retain?
a. 0.47%
b. 0.18%
c. 0.25%
d. 0.33% - What wash rate would be required in a single classifier in order to
wash the sand to the same extent?
a. 0.5 kg/s
b. 0.8 kg/s
c. 0.4 kg/s
d. 0.9 kg/s
- C. 0.25%
- B. 0.8 kg/s
When the solvent dissolves very little of solute, then
a. solvent of low latent heat of vaporization should be used.
b. solvent of low freezing point should be used.
c. large quantity of solvent is required to extract the solute.
d. very small quantity of solvent is required.
C. large quantity of solvent is required to extract the solute.
Seeds, containing 20% by mass of oil, are extracted in a counter
current plant, and 90% of the oil is recovered in a solution
containing 50% by mass of oil. If the seeds are extracted with
fresh solvent and 1 kg of solution is removed in the underflow in
association with every 2 kg of insoluble matter, how many ideal
stages are required?
a. 5
b. 3
c. 7
d. 2
A. 5
Ground roasted coffee contains 8% soluble solids, 2% water, and
90% inert insoluble solids. In order to obtain an extract with high
soluble solids content without having to concentrate it for spray
drying, a countercurrent extraction process is to be used to
prepare the extract. It is desired that the final extract contains 0.15
kg soluble/ kg water and that the soluble of the spent coffee
grounds not to exceed 0.008 kg/kg dry inert solids. The coffee
grounds carry 1 kg water/ kg of soluble free inert solids and this
quantity is constant with the solute concentration in the extract.
Determine the number of extraction stages needed for this
process.
a. 3
b. 4
c. 5
d. 6
D. 6
Leaching of uranium ore and gold ore is done in
a. centrifugal extractor
b. Bollman extractor
c. Pachuka tanks
d. none of these
C. Pachuka tanks
Tung meal containing 55% oil is to be extracted at a rate of 4000
kg/hr using n-hexane containing 5% wt oil as solvent. A counter current multiple stage extraction system is to be used. The meal
retains 2 kg solvent per kg of oil free meal while the residual
charge contains 0.11 kg oil per kg oil free meal while the product
is composed of 15 weight percent of oil. The theoretical number
of stages is
a. 4
b. 5
c. 3
d. 6
A. 4
Bollman extractor
a. is a static bed leaching equipment.
b. is used for extraction of oil from oil seed.
c. is a centrifugal extractor.
d. employs only counter-current extraction.
B. is used for extraction of oil from oil seed.
One thousand pounds of roasted copper ore containing 10
percent CuSO4, 85 percent insoluble gangue and 5 percent
moisture is to be extracted by washing it three times with 2000-lb
batches of fresh water. It has been found that the solids retain 0.8
lb of solution per pound of gangue.
- What is the percent CuSO4 of the final underflow sludge after
three washings?
a. 0.13%
b. 6.54%
c. 3.12%
d. 8.90% - What is the percent recovery?
a. 75.5%
b. 90.8%
c. 85.1%
d. 97.9%
- A. 0.13%
- D. 97.9%
Acetic acid will be most economically separated from a dilute
solution of acetic acid in water by
a. solvent extraction
b. evaporation
c. continuous distillation
d. absorption
A. solvent extraction
Separation of two or more components of a liquid solution cannot
be achieved by
a. liquid extraction
b. absorption
c. fractional crystallization
d. evaporation
b. absorption
Solvent extraction is the terminology applied to the liquid-liquid
extraction, which is preferred for the separation of the
components of liquids, when
a. extracting solvent is cheaply and abundantly available.
b. one of the liquid components is heat sensitive.
c. viscosity of liquid components is very high.
d. one of the liquid components has very high affinity towards the
solvent.
d. one of the liquid components has very high affinity towards the
solvent.
The distribution coefficient of solute A between solvents B and S
is given by Y = 2.5X where Y = mass of A / mass of S in extract
and X = mass of A / mass of B in raffinate. S and B are mutually
immiscible. A solution containing 25% A in B is to be extracted in
a single stage contact with a recovery of 80%. The amount of S
in kg required per 100 kg of solution is nearly
a. 100
b. 150
c. 120
d. 200
C. 120
The solvent used in liquid extraction should not have high latent
heat of vaporization, because
a. the pressure drop and hence the pumping cost will be very
high.
b. it cannot be recovered by distillation.
c. its recovery cost by distillation may be prohibitively high.
d. it will decompose while recovering by distillation.
c. its recovery cost by distillation may be prohibitively high.
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 = 2x, 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
a. 25%
b. 70%
c. 50%
d. 90%
c. 50 %
Which of the following equipment is not used in liquid-liquid
extraction?
a. Pachuka tank
b. Packed towers
c. Agitated vessels
d. Centrifugal extractors
a. Pachuka tank
A liquid mixture of acetaldehyde and toluene contains 8 lb of
acetaldehyde and 90 lb of toluene. Part of the acetaldehyde in
this solution is to be extracted using pure water as the extracting
agent. The extraction is to be performed in two stages, using 25
lb of fresh water for each stage. The raffinate layer from the first
stage is treated by fresh water in the second stage. The extraction
takes place at 170C and the equilibrium equation Y=2.2X may be
employed. Assuming toluene and water is immiscible, what would
be the weight percent of acetaldehyde in a mixture of the extracts
from both stage if each of the extraction were theoretically
perfect?
a. 8.96%
b. 7.10%
c. 9.33%
d. 5.52%
A. 8.96%
Which of the following is an undesirable property for an absorbing
solvent?
a. Low vapor pressure
b. Low freezing point
c. Low viscosity
d. None of these
d. None of these
The solubility of iodine per unit volume is 200 times greater in
ether than in water at a particular temperature. If an aqueous
solution of iodine, 30 ml in volume and containing 2 mg of iodine
is shaken with 30 ml of ether and the ether is allowed to separate,
- What quantity of iodine remains in the water layer?
a. 9.95x10-3 mg
b. 6.05x10-3 mg
c. 8.86 x10-3 mg
d. 5.40 x10-3 mg
- What quantity of iodine remains in the water layer if only 3 ml of
ether is used?
a. 0.086 mg
b. 0.072 mg
c. 0.095 mg
d. 0.063 mg - How much iodine is left in the water layer if the extraction in (1)
is followed by a second extraction, again using 3 ml of ether?
a. 4.53x10-3 mg
b. 1.37x10-3 mg
c. 2.09 x10-3 mg
d. 2.88 x10-3 mg
- A. 9.95x10-3 mg
- C. 0.095 mg
- A. 4.53x10-3 mg
Which method is more efficient, a single large washing or repeated small washing?
a. single large washing
b. repeated small washing
c. either single large or repeated small washing
d. none of these
b. repeated small washing
A solution of solute (A) in diluent (B) is mixed with solvent (S).
The component (B) is slightly soluble in (S). The resulting extract
will be
a. rich in S, poor in B, poor in A
b. poor in S, rich in B, poor in A
c. rich in S, rich in B, rich in A
d. rich in S, poor in B, rich in A
d. rich in S, poor in B, rich in A
The apex of an equilateral-triangular coordinate (in ternary liquid
system) represents a/an
a. pure component
b. ternary mixture
c. binary mixture
d. insoluble binary system
a. pure component
Sides of equilateral-triangular co-ordinates (on which ternary
liquid system is plotted) represent
a. a pure component.
b. a binary mixture.
c. a ternary mixture.
d. partially miscible ternary system.
b. a binary mixture.
In triangular coordinates, the ternary composition point falls
__________ of the triangle.
a. in the corners
b. on the sides
c. inside
d. none of these
c. inside
For numbers 38 to 39:
A solution of 5% acetaldehyde in toluene is to be extracted with
water in a five-stage concurrent unit. If 25 kg water per 100 kg of
feed is used, calculate the following:
- The mass of acetaldehyde extracted if the equilibrium relation is
given by: kg acetaldehyde per kg water = 2.20 (kg acetaldehyde
per kg toluene).
a. 4.49 kg / 100 kg feed
b. 1.11 kg / 100 kg feed
c. 3.36 kg / 100 kg feed
d. 2.98 kg / 100 kg feed
- The final concentration in % weight
a. 0.89%
b. 0.67%
c. 0.54%
d. 0.33%
- a. 4.49 kg / 100 kg feed
- c. 0.54%
The commonly used solvent in supercritical extraction is
a. methyl ethyl ketone
b. carbon tetrachloride
c. water
d. carbon dioxide
d. carbon dioxide
To plan a liquid–liquid extraction we need to know the solute’s
distribution ratio between the two phases. One approach is to
carry out the extraction on a solution containing a known amount
of solute. After extracting the solution, we isolate the organic
phase and allow it to evaporate, leaving behind the solute. In one
such experiment, 1.235 g of a solute with a molar mass of 117.3
g/mol is dissolved in 10.00 mL of water. After extracting with 5.00
mL of toluene, 0.889 g of the solute is recovered in the organic
phase. How many extractions will we need to recover 99.9% of
the solute?
a. 5
b. 6
c. 8
d. 4
b. 6
By extraction with amyl acetate, Penicillin F is recovered from an
aqueous fermentation broth using 6 volumes of solvent per 100
volumes of the aqueous phase. At pH = 3.2, the distribution
coefficient KD is 80.
- What fraction of the penicillin would be recovered in a single ideal
stage?
a. 77%
b. 65%
c. 83%
d. 92%
- What would be the recovery with two-stage extraction using fresh
solvent in both stages?
a. 88%
b. 97%
c. 75%
d. 69%
- c. 83%
- b. 97%
Which of the following equipment is not used for liquid
dispersion?
a. Wetted wall towers
b. Packed tower
c. Venturi scrubbers
d. Agitated vessels
c. Venturi scrubbers
In a counter-current liquid extractor
a. both liquids flow at fixed rate.
b. both liquids can have any desired flow rate.
c. only one of the liquids may be pumped at any desired rate.
d. liquid’s flow rate depends upon the temperature and pressure.
c. only one of the liquids may be pumped at any desired rate.
The equipment used in the extraction of highly corrosive
radioactive liquids is
a. pulse column
b. mixer settler
c. spray column
d. baffle tower
a. pulse column
Radioactive nuclear waste is treated in
a. mixer-settler extractor
b. rotating-disc contactor
c. pulsed column extractor
d. Bollman extractor
c. pulsed column extractor
Benzoic acid is 9 times more soluble in chloroform than in water.
The percent benzoic acid that will remain from a water solution of
benzoic acid if
- Equal quantity of chloroform and water is used is
a. 10%
b. 20%
c. 15%
d. 30%
- Twice as much as chloroform as water is used
a. 2.6%
b. 5.3%
c. 3.5%
d. 6.0%
- If extraction as in Problem 1 were followed by an extraction as
in Problem 2 is
a. 0.53%
b. 0.35%
c. 0.63%
d. 0.73%
- a. 10%
- c. 5.3%
- a. 0.53%
Antibiotics are best handled in a
a. Podbielniak extractor
b. sieve tray contractor
c. rotating disc contactor
d. pulsed column extractor
a. Podbielniak extractor
__________ extractor uses centrifugal force for separating the
two phases.
a. Treybal
b. Podbielniak
c. Schiebel
d. none of these
b. Podbielniak
Desulfurization of petrol is done in a
a. Bollman extractor
b. rotating disc extractor
c. packed extraction column
d. plate type extraction column
b. rotating disc extractor
Which of the following is the most suitable for extraction in a
system having very low-density difference?
a. Mixer-settler extractor
b. Centrifugal extractor
c. Pulsed extractor
d. Packed extraction tower
b. Centrifugal extractor
Which of the following solutions will follow Raoult’s law most
closely?
a. A solution of benzene, toluene and o-xylene
b. 35% solution of camphor in water
c. 35% solution of NH3 in water
d. A solution of polar organic compounds (not of homologs of a
series).
a. A solution of benzene, toluene and o-xylene
Calculate the equilibrium compositions of the liquid and the vapor
phases for the mixture of methyl alcohol in water at a temperature
of 500C and under a pressure of 40 kPa. Assume that both the
liquid and the vapor behave ideally. At 500C, the vapor pressure
of methyl alcohol is 53.32 kPa and that of water is 12.33 kPa.
a. 67.5% methyl alcohol in liquid and 89.98% methyl alcohol in
vapor
b. 50.2% methyl alcohol in liquid and 77.60% methyl alcohol in
vapor
c. 61.1% methyl alcohol in liquid and 62.12% methyl alcohol in
vapor
d. 54.6% methyl alcohol in liquid and 94.33% methyl alcohol in
vapor
a. 67.5% methyl alcohol in liquid and 89.98% methyl alcohol in
vapor
Determine the composition of the equilibrium vapor over a liquid
mixture consisting of 10 mol % water, 50 mol % acetic acid and
40 mol % acetone at 800C, assuming that the component obey
Raoult`s law. The vapor pressures of components at 800C are: water – 47.33 kPa, acetic acid – 27.32 kPa and acetone – 219.77
kPa.
a. 2.55% water, 10.35% acetic acid and 87.10% acetone
b. 4.45% water, 12.85% acetic acid and 82.70% acetone
c. 3.50% water, 15.00% acetic acid and 81.50% acetone
d. 5.60% water, 11.75% acetic acid and 82.65% acetone
b. 4.45% water, 12.85% acetic acid and 82.70% acetone
A binary mixture of two moles benzene and 8 moles of toluene
will boil at
a. 110 0C
b. 105 0C
c. 110 0F
d. 102 0C
d. 102 0C
Boiling point diagram is
a. not affected by pressure.
b. affected by pressure.
c. a plot of temperature vs. liquid composition.
d. a plot of temperature vs. vapor composition.
b. affected by pressure.
A 50 % by weight benzene – toluene mixture is fed to a column at 180 0F and 1 atm. The condition of the feed is called
a. saturated liquid
b. sub cooled liquid
c. saturated vapor
d. mixture of liquid and vapor
b. sub cooled liquid
The percentage change in the boiling point of a 20 mole benzene
– toluene solution when the pressure is increased from 1 atm to
2 atm is
a. 10.5 % increase
b. 25.5 % increase
c. 25.5 % decrease
d. 10.5% decrease
c. 25.5 % decrease
The ease of difficulty of separating components by distillation is
determined by the
a. relative volatility
b. viscosity
c. mole fraction
d. weight fraction of the components
a. relative volatility
When the liquid phase and vapor phase of a binary system obeys
Raoult’s and Dalton’s law respectively, the relative volatility is the
ratio of
a. vapor pressure of component A to that of component B.
b. vapor pressure of component A to the total pressure.
c. vapor pressure of component A to the partial pressure of A.
d. partial pressure of component A to the total pressure.
a. vapor pressure of component A to that of component B.
Relative volatility varies with the concentration of component for
an ideal solution. The relative volatility of a binary mixture may be
defined as the ratio of vapor pressure of component ‘A’ to that of
component ‘B’, when
a. only vapor phase follows Raoult’s law.
b. only liquid phase obeys Dalton’s law.
c. liquid phase obeys Dalton’s law and vapor phase obeys
Raoult’s law.
d. Vapor phase obeys Dalton’s law and liquid phase obeys
Raoult’s law.
d. Vapor phase obeys Dalton’s law and liquid phase obeys
Raoult’s law.
The-relative volatility for separation of a non-ideal binary mixture
by distillation should be
a. 0
b. > 1
c. 1
d. < 1
A liquid mixture of ethyl alcohol and water is in equilibrium with a
vapor containing ethyl alcohol and water at a total pressure of 760
mmHg. A sample of the vapor indicates that it contains 3.3 mol of
ethyl alcohol for every 1.7 mol of water. If the liquid has a mol
fraction of 0.52 ethyl, what is the relative volatility for the mixture?
a.1.59
b.1.79
c. 1.69
d. 1.89
The physical separation of components in a miscible mixture by
simultaneous evaporation and condensation is
a. absorption
b. drying
c. extraction
d. distillation
d. distillation
In a batch distillation, the boiling point of the distillate product
compared to the residue is
a. the same
b. higher
c. lower
d. half
c. lower
In batch distillation with constant reflux, overhead product
composition __________ with time.
a. increases
b. decreases
c. does not vary
d. may increase on decrease, depends on the system.
b. decreases
Increasing the operating pressure of a distilling column
a. does not make a difference in components separation
b. makes separation difficult
c. sharpens separation
d. requires less heat in the feed heater
b. makes separation difficult
Determine the relative volatility of n-butane/n-pentane mixture at
300C and 1 atm abs
a. 2.55
b. 3.04
c. 3.46
d. 4.28
c. 3.46