Engineering Chemistry MCQ’S Unit-1

WATER AND ITS TREATMENT

HARDNESS OF WATER – TYPES – EXPRESSION OF HARDNESS

1.Hardness of water is due to the presence of
salts of
a) Potassium
b) Chlorine
c) Magnesium
d) Boron
Answer: c
Explanation: Hardness of water is due to the
presence of salts of calcium and magnesium.
Hard drinking water may have moderate
health benefits, but can pose serious problems
in industrial settings, where water hardness is
monitored to avoid costly breakdowns in
boilers, cooling towers, and other equipment
that handles water.
2.Select the incorrect statement from the
following option.
a) Water which does not form lather with
soap and forms white scum is called hard
water
b) Hard water contains dissolved calcium and
magnesium salts in it
c) In hard water, cleansing quality of soap is
depressed
d) Due to the presence of dissolved hardnessproducing salts, the boiling point of water is
depressed
Answer: d
Explanation: Due to the presence of
dissolved hardness-producing salts, the
boiling point of water is elevated. Elevation
in boiling point is one of the most important
colligative property. All the other options are
correct.
3.Select the incorrect statement from the
following option.
a) Permanent hardness is due to dissolved
chlorides and sulphates of calcium and
magnesium
b) It can be removed by mere boiling of water
c) It is also known as non-alkaline hardness
d) The difference between the total hardness
and the alkaline hardness gives the nonalkaline hardness
Answer: b
Explanation: Unlike temporary hardness,
permanent hardness is not destroyed on
boiling. Varoius methods are adopted for the
removal of permanent hardness like zeolites,
lime-soda process etc. All the other options
are correct.
4.Alkaline hardness is due to the presence of
bicarbonate, carbonate and hydroxides of the
hardness-producing metal ions.
a) True
b) False
Answer: a
Explanation: Alkaline hardness is due to the

presence of bicarbonate, carbonate and
hydroxides of the hardness-producing metal
ions. This is also called carbonate hardness. It
is temporary and can be removed easily by
boiling.

5.Select the incorrect statement from the
following option.
a) The taste of hard water is better than soft
water
b) The dissolved calcium in hard water can
help to produce strong teeth
c) Hard water coats the lead piping with a
layer of insoluble calcium carbonate which
prevents poisonous lead dissolving in water
d) Boiler feed water should also be hard in
nature

Answer: d

Explanation: Boiler feed water should be free from hardness otherwise explosion may occur. All the other options are correct. The taste of hard water is better than soft water and dissolved calcium in hard water can help to produce strong teeth. Hard water coats the lead piping with a layer of insoluble calcium carbonate which prevents poisonous lead dissolving in water.

6.Hardness of water is conventionally
expressed in terms of equivalent amount of
a) H2CO3
b) MgCO3
c) CaCO3
d) Na2 CO3
Answer: c
Explanation: Hardness of water is
conventionally expressed in terms of
equivalent amount of CaCO₃
. The total water
hardness is the sum of the molar
concentrations of Ca²⁺ and Mg²⁺, in mol/L or
mmol/L units.
7.The chemical equivalent of MgSO₄ salt is

a) 60
b) 47.5
c) 82
d) 68
Answer: a
Explanation: The molar mass of MgSO4 is
120 and its n-factor is 2. So, chemical
equivalent = Molar mass/ n-factor = 60.

8.Which of the following is not a unit of
hardness?
a) Parts per million
b) Degree centigrade
c) Degree clarke
d) Degree French
Answer: b
Explanation: Degree centigrade is not a unit
of hardness. Degree centigrade is the unit of
temperature. The unit for hardness is ppm
(parts per million), degree clarke and degree
french. All these three units are inter-related.

9.1 degree Clarke = 1 part of CaCO₃ per ___________parts of water.

a) 10,000
b) 30,000
c) 50,000
d) 70,000
Answer: d
Explanation: 1 degree Clarke = 1 part of
CaCO₃ per 70,000 parts of water. It is
calculated mathematically.

10.1 ppm =
a) 0.07 ⁰Fr
b) 0.7⁰Fr
c) 0.1⁰Fr
d) 0.01⁰Fr
Answer: c
Explanation: 1 ppm = 0.1⁰Fr. It is calculated
mathematically.

11.How many grams of MgCO₃ dissolved
per litre gives 84 ppm hardness?
a) 70.56 mg/L
b) 48.23 mg/L
c) 81.49mg/L
d) 66.12 mg/L
Answer: a
Explanation: 70.56 mg/L of MgCO₃
dissolved per litre gives 84 ppm hardness.
12.EDTA method for hardness determination
is a less accurate and inconvenient procedure.
a) True
b) False
Answer: b
Explanation: EDTA method for hardness
determination is a more accurate, convenient
and rapid procedure. Ethylene
diaminetetraacetic acid (EDTA), is an amino
poly-carboxylic acid and a colorless, watersoluble solid.

ESTIMATION OF HARDNESS OF WATER BY EDTA

1.Estimation of hardness can be determined
by types.
a) 2
b) 3
c) 4
d) 5
Answer: a
Explanation: Estimation of hardness can be
determined by two types. They are Soap
titration method and EDTA method.

2.Total hardness of water can be determined
by titrating the fixed volume of water against
the standard solution.
a) Soap
b) Alkaline soap

c) Acidic soap
d) Alcoholic soap
Answer: d
Explanation: Total hardness of water can be
determined by titrating the fixed volume of
water against the standard alcoholic soap
solution.

3.The end point of the titration in the soap
titration method is
a) Formation of lather
b) Formation of salts
c) Formation of carbonates
d) Formation of bicarbonates
Answer: a
Explanation: The end point of the titration in
the soap titration method is at the formation
of lather that stands for about two minutes.
4.The sodium soap will precipitate all the
hardness causing ions into their respective
a) Carbonates
b) Bicarbonates
c) Stereates
d) Chlorides
Answer: c
Explanation: The sodium soap will
precipitate all the hardness causing ions into
their respective stereates in the beginning of
the soap titration method.
5.The water which form lather directly with
the soap is called
a) Hard water
b) Soft water
c) Partially hard water
d) Very hard water
Answer: b
Explanation: The water which forms lather
directly with the soap is called soft water. The
water which forms precipitates when reacted
with soap is called as the hard water.

6.EDTA method is also called as
a) Complexometric titration
b) Complex titration
c) Complement titration
d) Complexion titration
Answer: a
Explanation: EDTA method is also called as
the complexometric titration. In EDTA
method is ethylene diamine tetra acetate is the
compound used to remove the hardness.
7.The indicator used in the EDTA method is
a) Benzene
b) Phenopthalene
c) Ethylene diamine
d) Erichrome black T
Answer: d
Explanation: The indicator used in the EDTA
method is erichrome black T. The hardness
causing ions like Ca++ and Mg++ forms the
unstable complexes with reacting the
erichrome black T.
8.EDTA has the ability to form
with metal ions.
a) Stable complexes
b) Unstable complexes
c) Salts
d) Acids
Answer: a
Explanation: EDTA has more affinity to
form stable complexes by reacting with metal
ions. The EDTA forms the stable EDTA
complexes.
9.The colour of dye metal complex and dye
are
a) Same
b) Different
c) Same in only some cases
d) Cannot be known
Answer: b
Explanation: The colour of dye metal
complex and dye are different. EDTA extracts
the metal ions from the metal ion dye to form
stable complex.
10.The change in colour is sharper at the PH
of
a) 5
b) 10
c) 15
d) 20
Answer: b
Explanation: The change in the colour of the
ions is sharper at the PH of the 10 than that of
the other ranges of the PH.
11.At PH=10, the metal dye complex has the
colour
a) Wine red
b) Blue
c) Green
d) Pink
Answer: a
Explanation: At the PH=10, the metal dye
complex ion has the colour is wine red but the
dye itself has the blue colour at the PH of 10.
12.To prepare EDTA solution
grams of EDTA is dissolved in the one liter of
water.
a) 1
b) 2
c) 3
d) 4
Answer: d
Explanation: To prepare EDTA solution, four
grams of the EDTA is dissolved in the one
liter of the water. This is the standard EDTA
solution used to determine the hardness of
water.

13.drops of indicator is used in the EDTA method.
a) 1 to 2 drops
b) 2 to 3 drops

c) 2 to 4 drops
d) 5 to 8 drops
Answer: a
Explanation: 1 to 2 drops of the indicator is
used in the EDTA method. 0.5gms of the dye
is dissolved into the 100ml of alcohol and the
indicator of two to three drops is added.

14.The buffer used in the EDTA solution
must have the PH of
a) 20
b) 15
c) 10
d) 5
Answer: c
Explanation: The buffer used in the EDTA
solution must have the PH of 10. Freshly
prepared solutions are more affective to have
the accurate results.
15.The standard hard water is prepared such
that each ml must contain mg of
CaCO₃.
a) 1
b) 2
c) 3
d) 24
Answer: a
Explanation: The 1g of pure CaCO₃ is
dissolved in the minimum amount of
concentrated HCL diluted to 1ltr of distilled
water such that it contains 1mg of CaCO₃.

BOILER TROUBLES (SCALE AND SLUDGE) – TREATMENT OF BOILER FEED WATER – INTERNAL TREATMENT (PHOSPHATE, COLLOIDAL, SODIUM ALUMINATE AND CALGON CONDITIONING). EXTERNAL TREATMENT

1.Water is mainly used in boilers for the
generation of
a) Power
b) Electricity
c) Steam
d) Current
Answer: c
Explanation: Water is mainly used in boilers
for the generation of steam. This steam is
further used in the power plants for the
generation of electricity.
2.Which of the following should not be a
composition of boiler-feed water?
a) Hardness should be below 0.2ppm
b) Its caustic alkalinity should lie between
0.15 to 0.45 ppm
c) Its soda alkalinity should be 0.45-1 ppm
d) Its caustic alkalinity should be 1.5-2 ppm
Answer: d
Explanation: Its caustic alkalinity should be
0.15-0.45 ppm. All the other options are
correct. Hardness should be below 0.2ppm,
caustic alkalinity should lie between 0.15 to
0.`rt45 ppm and soda alkalinity should be 0.45-
1 ppm.
3.Which of the following is not a result of
the excess of impurity in boiler-feed?
a) Scale and sludge formation
b) Decomposition
c) Corrosion, priming and foaming
d) Caustic embrittlement
Answer: b
Explanation: Excess of impurities in boilerfeed results in scale and sludge formation,
corrosion, priming, foaming and caustic
embrittlement. It does not contribute to the
decomposition process.
4.If the precipitate formed is soft, loose and
slimy, these are and if the
precipitate is hard and adhering on the inner
wall, it is called
a) Sludges, scale

b) Scale, sludges
c) Sludges, rodent
d) Scale, rodent
Answer: a
Explanation: If the precipitate formed is soft,
loose and slimy, these are sludges and if the
precipitate is hard and adhering on the inner
wall, it is called scale. A rodent is a small
furry mammal whose teeth never stop
growing.

5.Which of the following option is incorrect
about the sludges?

a) Sludges are soft, loose and slimy
precipitate
b) They are non-adherent deposits and can be
easily removed
c) Formed generally at heated portions of the
boiler
d) Can be removed by blow down operation
Answer: c
Explanation: Sludges are formed generally at
colder portions of the boiler. All the other
options are correct. Sludges are soft, loose
and slimy precipitate, non-adherent deposits
and can be easily removed by blow down
operation.

6.The scales decrease the efficiency of boiler
and chances of explosions are also there.
a) True
b) False
Answer: a
Explanation: The scales decrease the
efficiency of boiler and chances of explosions
are also there. Scale is the precipitate that is
hard and adhering on the inner wall.

7.The propulsion of water into steam drum
by extremely rapid, almost explosive boiling
of water at the heating surface is called
a) Foaming
b) Priming

c) Corrosion
d) Caustic embrittlement
Answer: b
Explanation: The propulsion of water into
steam drum by extremely rapid, almost
explosive boiling of water at the heating
surface is called priming. Priming is
necessary as it removes all the air voids from
the passage of water.

8.The phenomenon during which the boiler
material becomes brittle due to accumulation
of caustic substances is known as

a) Foaming
b) Priming
c) Corrosion
d) Caustic embrittlement

Answer: d
Explanation: The phenomenon during which
the boiler material becomes brittle due to
accumulation of caustic substances is known
as caustic embrittlement. This can be
prevented by using sodium phosphate instead
of sodium carbonate as softening reagents.

9.Foaming is caused by the formation of
a) Acids
b) Alcohols
c) Oils and alkalis
d) Ketones
Answer: c
Explanation: Foaming is caused by the
formation of oils and alkalis. Oils and Alkalis
becomes sticky and greasy on the surface and
hence results in foaming.

10.Corrosion is the decay or disintegration of
boiler body material either due to chemical or
electrochemical reaction with environment.
a) True
b) False

Answer: a
Explanation: Corrosion is the decay or
disintegration of boiler body material either
due to chemical or electrochemical reaction
with environment. It converts a refined metal
to a more stable form, such as its oxide,
hydroxide, or sulphide.

ION EXCHANGE PROCESS

1.Ion exchange process is also called as
a) Permutit’s process
b) Demineralization
c) Zeolite process
d) Lime soda process
Answer: b
Explanation: Ion exchange process is also
called as the demineralization. The zeolite
process is otherwise called as the ion
exchange process.
2.The operational cost of the ion exchange
process is
a) High
b) Low
c) Very high
d) Very low
Answer: b
Explanation: The capital cost of the ion
exchange process is very high. The
operational cost of the ion exchange process
is about low.
3.The hardness in the ion exchange process
is reduced to
a) 0-1ppm
b) 0-2ppm
c) 0-3ppm
d) 0-4ppm
Answer: b
Explanation: The hardness of the ion
exchange process is reduced to 0 to 2ppm. It
is a very effective method to reduce the
hardness of the water.
4.The total are removed
completely in the ion exchange process.
a) Dissolved gases
b) Dissolved solids
c) Dissolved solvents
d) Dissolved other impurities
Answer: b
Explanation: The total dissolved solids are
removed completely in the ion exchange
process. In lime soda process, the total
dissolved solids are reduced only.
5.In ion exchange process, the iron and
manganese ions are removed from the water.
a) True
b) False
Answer: a
Explanation: In ion exchange process, not
only iron and manganese ions are removed
from the water but also all the cations are
removed.
6.Water softened during method
will be ideal in boilers.
a) Zeolite method
b) Lime soda method
c) Demineralisation method
d) Permutit’s process
Answer: b
Explanation: Water softened during the
demineralisation method is completely free
from all the impurities and flaws. So, the
water after the softening by this method will
be ideal for boilers.

7.Ion exchange process is the clean process
because it has
a) Sludge formation
b) No sludge formation
c) Little sludge is formed
d) Other precipitates are formed

Answer: b
Explanation: In ion exchange process, there
is no formation of sludge. So, it is called as
the clean process

8.The regeneration of acids and alkalis in ion
exchange process is
a) Cheaper
b) Costlier
c) Time taking
d) Hard process
Answer: b
Explanation: The one of the disadvantages of
the ion exchange process is the regeneration
of the acids and alkalis in ion exchange
process is costlier.
9.In ion exchange process, the cation
exchange resin is generated by passing
a) Acids
b) Dilute acids
c) Alkalis
d) Dilute alkalis
Answer: b
Explanation: In ion exchange process, the
cation exchange resin is generated by passing
the dilute acids. The anion exchange resin is
generated by passing alkali.
10.In the case of the zeolites, ion exchange
process do not function properly because of
the
a) Turbidity
b) Suspended matter
c) Turbidity and suspended matter
d) Neither turbidity nor suspended matter
Answer: c
Explanation: In case of zeolites, ion
exchange process do not function properly
because of the turbidity and suspended matter
as they send to cover the surface of the resin.
11.The initial equipment in the ion exchange
process is
a) More
b) Less
c) Very less
d) Very high
Answer: a
Explanation: The initial equipment in the ion
exchange process is more. Continuous supply
of softened water can be made available by
providing storage facilities.
12.The residual hardness after the treatment
of water is about
a) 1 ppm
b) Less than 1ppm
c) 2 ppm
d) Less than 2pmm
Answer: d
Explanation: The residual hardness after the
treatment of the water is about less than
2ppm. So, they are suitable for the high
pressure boilers.
13.The continuous supply of soft water can
be provided by having
a) Storage facilities
b) Required amount of ppm
c) High pressure boilers
d) 1ppm
Answer: a
Explanation: The continuous supply of soft
water can be provided by having storage
facilities and also two columns of each resin.
14.The cost of the resins used in the ion
exchange process is
a) High
b) Low
c) Moderate
d) Depends on water
Answer: a
Explanation: The cost of the resins used in
the ion exchange process is high and the
regeneration of the resins in also a costly
process.

15.The mineral free water is not used in
a) Pharmaceuticals
b) Cosmetics
c) Explosives
d) Drinking
Answer: d
Explanation: In drinking water some
minerals must be present. In pharmaceuticals,
cosmetics, explosives and in other
manufacturing processes, the mineral free
water is used.

ZEOLITE PROCESS

1.In which process of water softening, ion
exchange phenomenon takes place?
a) Lime soda process
b) Zeolite process
c) Boiling
d) Demineralization process
Answer: b
Explanation: In the zeolite process, calcium
and magnesium are removed from hard water
by ion exchange phenomenon.
2.In which process of water softening, the
chemicals are added to remove hardness from
water?
a) Lime soda process
b) Zeolite process
c) Boiling
d) Demineralization process
Answer: a
Explanation: In the Lime soda process, lime
and soda are added to remove temporary and
permanent hardness from water.
3.Zeolites are complex compound of
a) Aluminium and lime
b) Silica and soda
c) Aluminium, silica and soda
d) Lime and soda
Answer: c
Explanation: Zeolites are complex
compound of Aluminium, silica and soda. It
has the property of removing calcium and
magnesium from water and substituting
sodium in their place.
4.The color of the artificial zeolite permutit is
a) Grey
b) Yellow
c) Green
d) White
Answer: d
Explanation: The artificial zeolite permutit
has a large and lustrous grain. They are white
in color and has an appearance of coarse
sand.
5.Natural zeolite is mainly processed from
a) White sand
b) Green sand
c) Grey sand
d) Red sand
Answer: b
Explanation: The natural zeolite is mainly
processed from Green sand, which is also
called as Glauconite. It has lesser exchange
value than artificial zeolite.
6.The color of the natural zeolite is
a) Green
b) Grey
c) Black
d) Blue
Answer: a
Explanation: The color of the natural zeolite
is green as it is processed from Glauconite
which is green in color. It has an exchange
value of 6500-9000gm of hardness per m3 of
zeolite.

7.The chemical formula of Permutit is
a) SiOAl2O3Na2O
b) SiO2Al2O3Na2O
c) SiO2Al2O3NaO
d) SiO3Al2O3Na2O
Answer: b
Explanation: The chemical formula of
Permutit is SiO2Al2O3Na2O. The increase in
the value of SiO2 increases its resistance to
aggressive attacks.

8.Permutit has an exchange value of
grams of hardness per m3 of
zeolite.
a) 10,000
b) 20,000-30,000
c) 35,000-40,000
d) 40,000-50,000

Answer: c
Explanation: Permutit has an exchange value
of 35,000-40,000 grams of hardness per m3 of
zeolite. They absorb moisture from the atmosphere and should be kept in a dry place.

9.The thickness of the layers of filter sand of
zeolite softener is
a) 20cm
b) 30cm
c) 40cm
d) 100cm
Answer: d
Explanation: The thickness of the layers of
filter sand of zeolite softener lies in the range
of 75 to 150cm and their functioning is
similar to the rapid sand filter.
10.Which of the following is a disadvantage
of the zeolite process?
a) No sludge is formed
b) The process is almost automatic
c) Suspended impurities get deposited around

the zeolite particles
d) Zero hardness can be occurred
Answer: c
Explanation: The zeolite process is
unsuitable for highly turbid water where
suspended impurities get deposited around
the zeolite particles.

11.The zeolite process is unsuitable for water
containing iron and manganese.
a) True
b) False
Answer: a
Explanation: Iron and manganese bearing
water deposit hydroxides on the surface of
zeolite or react with zeolite to substitute iron
and manganese for sodium, which is an
irreversible reaction. This makes the zeolite
process unsuitable.

DESALINATION OF BRACKISH WATER

1.1.The example of brackish water is

a) Ground water
b) Rain water
c) Sea water
d) Underground water
Answer: c
Explanation: The example of brackish water
is sea water. Ground water, underground
water and rain water are not brackish water.
Sea water is also saline in nature and not fit
for domestic purpose.

2.Which of the following technique is not
used for the desalination of brackish water?
a) Electrolysis
b) Electrodialysis
c) Reverse osmosis
d) Distillation

Answer: a

Explanation: Electrolysis technique is not
used for the desalination of brackish water.
Electrodialysis, reverse osmosis and
distillation are the few techniques used for
desalination of brackish water.

3.Salt cannot be separated from brackish
water by freezing.
a) True
b) False
Answer: b
Explanation: Salt can be separated from
brackish water by freezing.
4.Electrodialysis is based on the fact that the
ions present in saline water migrate towards
their respective electrodes under the influence
of applied
a) Current
b) Resistance
c) Conductance
d) EMF
Answer: d
Explanation: Electrodialysis is based on the
fact that the ions present in saline water
migrate towards their respective electrodes
under the influence of applied emf. The
potential difference generated between the
elctrodes is the main cause of flow of
electrons.
5.The cation selective membrane is
embedded with functional groups of
a) Positive charge
b) Negative charge
c) Both positive as well as negative charge
d) Neutral
Answer: b
Explanation: The cation selective membrane
is embedded with functional groups of
negative charge as it attracts only positive
charges towards them.

6.6.In electrodialysis cell, the pressure is about

a) 2 kg/m2
b) 3 kg/m2
c) 5-6 kg/m2
d) 10 kg/m2
Answer: c
Explanation: Electrodialysis is an electrically
driven separation conducted at very low
pressure-driven of about 5-6 kg/m2
.

7.Electrodialysis is an electrically driven
separation conducted at a very low pressuredriven, size-exclusion filtering process.
a) True
b) False
Answer: a
Explanation: Electrodialysis is an electrically
driven separation conducted at a very low
pressure-driven, size-exclusion filtering
process. Electrodialysis is used to transport
salt ions from one solution through ionexchange membranes to another solution
under the influence of an applied electric
potential difference.
8.The ion-exchange membrane are
electrically conductive and are not permeable
to flow, even under pressure.
a) Electron
b) Oil
c) Fluorine
d) Water
Answer: d
Explanation: The ion-exchange membrane
are electrically conductive and impermeable
to water flow, even under pressure. Electrons
can easily flow through these membranes.
9.Select the incorrect statement from the
following option.
a) Electrodialysis reversal (EDR) was
introduced in the commercial sector to
improve electrodialysis process

b) The EDR process and conventional ED
unit operates on the same principle, except at
intervals of several times an hour
c) The reversal feature is useful in breaking
up films, scales and other deposits
d) Electrodialysis process is not economical
as per capital cost
Answer: d
Explanation: Electrodialysis process is
economical as per capital cost and operational
expenses are concerned. All the other options
are correct.

10.Which one of the following is not a cation
exchanger?
a) Amberlite
b) Triolite
c) Dowex
d) Duolite
Answer: b
Explanation: Triolite is not a cation
exchanger. Amberlite, dowex and duolite are
some of the examples of the cation exchanger.

REVERSE OSMOSIS.

1.The the salt rejection, the better
the system is performing.
a) Higher
b) Lower
c) Moderate
d) Poor
Answer: a
Explanation: The higher the salt rejection,
the better the system is performing. A low
salt rejection can mean that the membranes
require cleaning or replacement.
2.What is the osmotic pressure for sea water?
a) 1.5 Mpa
b) 1.8 Mpa
c) 2.3 Mpa
d) 2.45 Mpa

Answer: d
Explanation: The osmotic pressure of sea
water is 2.45 Mpa. The concentration of salt
in sea water is 32000-35000 mg/l. The
applied pressure on the RO equipment is 5.6-6.

3.Membrane permeation rate increases
proportionally to effective pressure.
a) True
b) False
Answer: a
Explanation: Although membrane
permeation rate increases proportionally to
effective pressure, the highest recommended
applied pressure of commercial membranes
presently available is 7.0 Mpa.
4.RO membranes are made of
a) Plastic
b) Cotton
c) Silk
d) Polymer
Answer: d
Explanation: The highest recommended
applied pressure of commercial membranes
presently available is 7.0 Mpa; beyond which
compaction will start to occur due to the fact
that RO membranes are made of polymers.
5.Concentrated seawater which is called
a) Permeate
b) Brine
c) RO water
d) Salt water
Answer: b
Explanation: When fresh water is separated
from seawater, concentrated seawater which
is called brine and is retained on the surface
of the RO membrane.
6.The osmotic pressure of the brine increases
proportionally to the salt concentration

a) True
b) False
Answer: a
Explanation: The salt concentration and the
osmotic pressure of the brine are related
proportionally, i.e., the osmotic pressure of
the brine increases as the salt concentration
increases.

7.The upper limit of brine concentration is
times the normal sea water.
a) 1.5
b) 2
c) 2.5
d) 3
Answer: c
Explanation: The upper limit of the brine
concentration is usually fixed. The upper
limit is normally 1.6-2.5 times that of the
normal seawater.
8.The water flux of RO membranes
as water viscosity lowers.
a) Increases
b) Decreases
c) Alters
d) Fluctuates
Answer: a
Explanation: When the water viscosity is
lowered, the water flux of RO membranes
increases and the water viscosity is lowered
by an increase in temperature. Thus, the
higher the temperature better is the flux.
9.What is the maximum acceptable limit of
temperature for RO?
a) 20˚C
b) 30˚C
c) 40˚C
d) 50˚C
Answer: c
Explanation: In order to reduce the effects of
temperature to a minimum, the acceptable
upper limit is 40°C. RO systems operate at
25°C usually.
10.What is the design temperature of RO
systems?
a) 20˚C
b) 25˚C
c) 30˚C
d) 35˚C
Answer: b
Explanation: RO systems are usually
designed to operate at 25°C and water flux
falls by 20–25 percent when water
temperature is lowered by 10°C.
11.What is the operating pH for RO systems?
a) 2-3
b) 4-6
c) 5-7
d) 8-9
Answer: c
Explanation: The pH of seawater is 8–8.5 in
general. The pH is reduced to 5-7 in order to
reduce scaling on the surface and chemical
deterioration of the RO membrane.
12.Calculate the number of membranes
required for the following data:
Flow: 535 m³/h.
Area: 400 m²
Flux considered: 12 lmh
a) 112
b) 115
c) 117
d) 120
Answer: a
Explanation: Number of membranes is
calculated based on the flow and area. Flux is
generally fixed based on the TDS present in
the raw water. Number of membranes = Flow
x 1000/flux/area. A number of membranes =
535/400/12=112.
13.Calculate the recovery for the following
data:

Product Flow: 535 m³/h.
Feed flow : 635 m³/h.
Flux considered: 12 lmh
a) 80%
b) 85%
c) 90%
d) 75%
Answer: b
Explanation: Recovery= Feed flow/Permeate
flow. In this case recovery is 85%. This is
arrived by 535/635*100=85%.

14.What is the thumb rule to consider for
osmotic pressure?
a) 1 psi for every 86 ppm of Na
b) 2 psi for every 86ppm of Na
c) 1 psi for every 43 ppm of Na
d) 2 psi for every 43 ppm of Na
Answer: a
Explanation: The tendency of a pure solution
constituting low solute concentration to flow
into solution constituting higher solute
concentration is known as osmosis. When
pressure greater than osmotic pressure is
applied then reverse osmosis takes place. The
thumb rule for the consideration of osmotic
pressure is 1 psi for every 86 ppm of Na.
15.What is the flux considered while
designing a reverse osmosis system for
treating RO permeate?
a) 30-40 LMH
b) 12-18 LMH
c) 20-25 LMH
d) 25-30 LMH
Answer: a
Explanation: Flux is the amount of water
flowing through a particular area. This is
dependent both on the nature of water and the
membrane surface area. The flux considered
for RO permeate is 30-40 LMH.
16.What is the flux considered while
designing a reverse osmosis system for
treating bore well water?
a) 30-40 LMH
b) 40-50 LMH
c) 20-30 LMH
d) 12-18 LMH
Answer: c
Explanation: The flux increases with
increase in pressure. It also increases with
increase in temperature. In case of bore well
water, the flux considered is 20-30 LMH.
17.What is the flux considered while
designing a reverse osmosis system for
treating surface water?
a) 15-22 LMH
b) 22-30 LMH
c) 12-15 LMH
d) 30-35 LMH
Answer: a
Explanation: The flux to be considered
depends on the nature of the water to be
treated. The flux is used to determine the
number of membranes required for the
treatment system. In the case of treating
surface water by a conventional method the
flux to be considered is 15-22 LMH.
18.What is the flux considered while
designing a reverse osmosis system for
treating surface water with UF system?
a) 15-20 LMH
b) 20-30 LMH
c) 12-15 LMH
d) 30-35 LMH
Answer: b
Explanation: The flux to treat surface water
by a conventional method and to treat by UF
differs. Conventional method includes Dual
media filters. In case the surface water is
treated by conventional, the flux considered
should be around 20-30 LMH.
19.How is Net driving pressure mathematically expressed?
a) Net driving pressure = P_f– 0.5 * D_P – Pp –
P_osmavg

b) Net driving pressure = 0.5 * DP –Pp –
Posmavg
c) Net driving pressure = Pf – 0.5 * DP – Pp
d) Net driving pressure = Pf * DP – Pp –
Posmavg
Answer: a
Explanation: Net driving pressure = Pf – 0.5^*DP – Pp -Posmavg. The net driving pressure is the pressure required to adequately sustain osmotic pressure. Here Pf is the feed pressure. DP is the pressure drop and Pp is the Permeate pressure.

Prabakaran S

Leave a Reply Cancel reply