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Multiple choice question for engineering

Set 1

1. The chemical formula of hypoiodous acid is
a) H2IO
b) H2I
c) HIO
d) HI2

View Answer

Answer: c [Reason:] The chemical formula of hypoiodous acid is HIO which is formed by the reaction of iodine with water and its chemical equation is I2 + H2O <=> HIO + H+ + I+.

2. At what pH, the dissociation of hypoiodous acid takes place?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: d [Reason:] The dissociation of hypoiodous acid takes place at pH= 4. HIO <=> H+ + IO.

3. What happens to the hypoiodous acid when the pH is over 8?
a) HIO is stable
b) Formation of hypoiodite ion takes place
c) Formation of iodine and hypoiodite ion takes place
d) Formation of iodine and iodate takes place

View Answer

Answer: d [Reason:] When pH is over 8, then HIO is unstable and will not form hypoiodite ion.Decomposition of hypoiodite ion takes place, resulting in formation of iodine and iodate.

4. The chemical formula of iodate is
a) HIO3
b) HIO
c) HIO2
d) H2IO2

View Answer

Answer: a [Reason:] The chemical formula of iodate is HIO3 which is formed when the pH during the decomposition of hypoiodite ion is over 8.

5. a HIO + b OH- <=> HIO3 + b H2O + b I. What are the values of a and b respectively in the above equation?
a) 1, 2
b) 1, 3
c) 3, 2
d) 3, 1

View Answer

Answer: c [Reason:] 3HIO + 2OH <=> HIO3 + 2 H2O + 2 I . This equation is formed when the pH is above 8 and where decomposition of hypoiodite ion takes place.

6. What happen to the concentration of iodine when the pH is between 6 and 8?
a) I2 decreases whereas HIO increases
b) I2 increases, whereas HIO decreases
c) Both I2 and HIO increases
d) Both I2 and HIO decreases

View Answer

Answer: a [Reason:] 3HIO + 2OH <=> HIO3 + 2 H2O + 2 I. When the pH is between 6 and 8, the percentage of iodine as I2 decreases while the percentage of iodine as HIO is increased.

7. State whether the following statement is true or false.
Iodine is a better disinfectant to kill virus than hypoiodous acid.
a) True
b) False

View Answer

Answer: b [Reason:] Hypoiodous acid destroys viruses at a considerably faster rate than I2 as iodine has little viricidal activity.

8. Ozone is a _______ allotrope of oxygen.
a) Monoatomic
b) Diatomic
c) Triatomic
d) Polyatomic

View Answer

Answer: c [Reason:] Ozone is a triatomic allotrope of oxygen, which is an unstable gas and the breakdown into normal oxygen containing two atoms of oxygen by molecule.

9. The ozone generators can convert ____ % of feed oxygen into ozone.
a) 1
b) 5
c) 1-4
d) 10

View Answer

Answer: c [Reason:] The ozone generators can convert 1-4 % of feed oxygen into ozone.They are used as an effective method to clean indoor air pollution and odors.

10. What happens during the breakdown of ozone?
a) CO2 is formed
b) Nascent oxygen is formed
c) CO2 and Nascent oxygen is formed
d) Formation of oxygen and water takes place.

View Answer

Answer: b [Reason:] During the breakdown of ozone, nascent oxygen is formed which contain a single atom of oxygen.

11. Which of the following is most effective in the killing of bacteria present in water?
a) Nascent oxygen
b) Chlorine
c) HOBr
d) I2

View Answer

Answer: a [Reason:] Nascent oxygen is very effective in oxidizing the organic matter and in the killing of bacteria present in the water which is formed during the breakdown of ozone.

12. The water is free from oxidizable materials. What is the dosage of ozone required?
a) 0.01ppm
b) 0.1-0.2ppm
c) 0.2-0.3ppm
d) 0.4-0.5ppm

View Answer

Answer: c [Reason:] A dosage of 0.2-0.3ppm is required to kill the coliform bacteria present in water which is free from oxidizable materials.

13. The dosage of ozone for municipal water treatment is
a) 0.5 ppm
b) 1ppm
c) 1.5 ppm
d) 2ppm

View Answer

Answer: c [Reason:] The dosage of ozone for municipal water treatment is 1.5ppm, which is not only used for disinfection but also it removes taste, color and odor from water.

Set 2

1. Consider the following variables.
1. Concentration of disinfectant
2. Concentration of organisms
3. Temperature
4. Time of contact
Disinfection is the function of which of the following variables?
a) 1, 2
b) 1, 2, 3
c) 1, 2, 3, 4
d) 2, 3, 4

View Answer

Answer: c [Reason:] The process of disinfection is the function of concentration of disinfectant, organisms, temperature of disinfection and time of contact.

2. According to which of the following, organism destroyed by disinfection is proportional to organism remaining?
a) Hazens equation
b) Chicks law
c) Darcy’s law
d) Rose equation

View Answer

Answer: b [Reason:] According to Chicks law of disinfection, the number of organisms destroyed in unit time is proportional to the number of organisms remaining.

3. Which of the following is the expression of Chicks law?
a) Dy/Dt = k (N – y)
b) Dy/Dt = k/(N – y)
c) Dy/Dt = k (N + y)
d) Dy/Dt = k (N * y)

View Answer

Answer: a [Reason:] The expression of Chicks law is given by Dy/Dt = k (N – y) Where, N is the number of organisms initially present, ‘y’ is the number of organisms remaining after time t and k is the coefficient of proportionality.

4. The integration of the expression of Chicks law is given by
a) N1/N = ekt
b) N1/N = kt
c) N1/N = k/t
d) N1/N = e-kt

View Answer

Answer: d [Reason:] According to Chicks law, Dy/Dt = k (N – y), by integration, loge N1/N = -kt = N1/N = e-kt Where, N1 = N – y.

5. The dimensional formula of rate constant used in Chicks law is
a) 1/t
b) 1/t2
c) 1/t3
d) t2

View Answer

Answer: a [Reason:] According to Chicks law, Dy/Dt = k (N – y) where, k is the rate of proportionality or rate constant having dimensional formula 1/t.

6. The number of organisms destroyed is equal to the number of organisms remaining at time t=
a) 0
b) 1
c) 2
d) 10

View Answer

Answer: a [Reason:] According to Chicks law, N1/N = e-kt, when t=0, N1/N = 1 or N1 = N, Where, N1 represents the remaining organisms.

7. The expression loge N1/N = – kt m Where, m is a constant such that m>1 represents
a) Rate of the kill will remains constant with time
b) Rate of the kill will increase with time
c) Rate of the kill will decrease with time
d) Rate of the kill is directly proportional to time

View Answer

Answer: b [Reason:] The expression loge N1/N = -ktm Where, m is a constant such that m>1 represents that rate of kill will increase with time whereas m<1 represents rate of the kill decrease with time.

8. For changing the concentration of disinfectant, the disinfecting efficiency is expressed by
a) C n *t p = Constant
b) C n/ t p = Constant
c) C q * Np = Constant
d) C q / Np = Constant

View Answer

Answer: a [Reason:] The disinfecting efficiency is expressed by C n *t p = Constant where, C is the concentration of disinfectant, t p is the time required to kill the organism and n is the coefficient of dilution.

9. The number of organisms in disinfection process can be expressed by
a) Cn *t p = Constant
b) C n/ tp = Constant
c) C q * Np = Constant
d) C q / Np = Constant

View Answer

Answer: c [Reason:] The number of organisms in disinfection process can be expressed by Cq * Np = Constant where, C is the concentration of disinfectant, the Np is the reduced concentration of organisms and q is the coefficient of disinfectant strength.

10. Efficiency of dilution decreases rapidly when the coefficient of dilution is
a) 0
b) 1
c) <1
d) >1

View Answer

Answer: d [Reason:] Efficiency of dilution decreases rapidly when the coefficient of dilution n is greater than 1 which is a measure of order of reaction.

11. When the coefficient of dilution is 1, then which of the following statement is correct?
a) Time of contact is more important than dosage
b) The dosage is more important than time of contact
c) Concentration and time are equally important
d) Efficiency of dilution decreases.

View Answer

Answer: c [Reason:] When the coefficient of dilution is 1, concentration and time are equally important and a first order will proceed.

12. State whether the following statement is true or false.
The temperature of disinfection is inversely proportional to the killing of organisms.
a) True
b) False

View Answer

Answer: b [Reason:] The temperature of disinfection is directly proportional to the killing of organisms and the increase in temperature results in a more rapid killing of organisms.

Set 3

1. The method of distribution of water is divided into how many types?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: c [Reason:] The method of distribution of water is divided into 3 types and it includes gravity system, pumping system and combined gravity and pumping system.

2. In which of the following distribution system, the clean water flows entirely under gravity?
a) Gravity system
b) Pressure system
c) Combined gravity and pumping system
d) Pumping system

View Answer

Answer: a [Reason:] The purified water in gravity system flow entirely under gravity. It is the most reliable and economical distribution system.

3. The pressure in the distribution mains does not depend on
a) Altitude to supply water
b) Fire fighting requirements
c) Availability of funds
d) Quality of water

View Answer

Answer: d [Reason:] The pressure in the distribution mains depends on the height to which water is required to be supplied, fire fighting requirements, whether the supply is metered or not and availability of funds.

4. The pressure in distribution mains in a residential building up to three storeys is
a) 2kg/cm2
b) 5kg/cm2
c) 7kg/cm2
d) 10kg/cm2

View Answer

Answer: a [Reason:] The pressure in distribution mains in a residential building up to three storeys is 2kg/cm2 and when it is between 3-6 storeys, the pressure is 3kg/cm2.

5. There is a 8 storey residential building in Lucknow. What is the pressure in the distribution mains?
a) 2kg/cm2
b) 5kg/cm2
c) 7kg/cm2
d) 10kg/cm2

View Answer

Answer: b [Reason:] When the height of residential building is between 6 to 10 storey, the pressure in the distribution mains lies between 4 to 5.5kg/cm2.

6. The velocity of water in a 10 cm diameter pipe should be
a) 0.2m/Sec
b) 0.5m/Sec
c) 0.9m/Sec
d) 1.2m/Sec

View Answer

Answer: c [Reason:] The velocity of water in a 10 cm diameter pipe should be 0.9m/Sec Which is 1.2m/Sec when the diameter of pipe is 15cm.

7. In which system of water supply, water is available for 24 hours but uneconomically used?
a) Continuous supply
b) Fixed supply
c) Intermittent supply
d) Low supply

View Answer

Answer: a [Reason:] In continuous water supply, water is wasted due to a continuous supply of water for 24 hours of the day or long duration of flow.

8. In which system of water supply, water is supplied only during fixed hours of the day?
a) Continuous supply
b) Fixed supply
c) Intermittent supply
d) Low supply

View Answer

Answer: c [Reason:] In Intermittent supply, water is supplied to the consumer during fixed hours of the day and is adopted when sufficient pressure is not available or sufficient quantity of water is not available.

9. The velocity of water in the pipe is 1.8m/Sec. What is the diameter of pipe used?
a) 10cm
b) 15cm
c) 25cm
d) 40cm

View Answer

Answer: d [Reason:] It is the maximum diameter of the pipe for which the velocity of water should not be less than 1.8m/Sec.

10. State whether the following statement is true or false.
The hourly demand rate is constant throughout the day.
a) True
b) False

View Answer

Answer: b [Reason:] The hourly demand rate is not constant throughout the day, it is more during morning and evening and less during other parts of the day.

11. According the mass curve method, the storage capacity is defined as
a) Maximum excess of supply / Maximum excess of demand
b) Maximum excess of supply * Maximum excess of demand
c) Maximum excess of supply – Maximum excess of demand
d) Maximum excess of supply + Maximum excess of demand

View Answer

Answer: d [Reason:] A mass curve of demand is the cumulative demand curve, which is obtained by continuously adding the hourly demands and plotting it against time.

12. _______ causes hoop tension in pipe shell.
a) Internal water pressure
b) External water pressure
c) Water hammer
d) Longitudinal stress

View Answer

Answer: a [Reason:] Internal water pressure causes hoop tension in pipe shell and its magnitude is given by f = pd/2t where p is the internal pressure of water, d is the diameter of the pipe and t is the thickness of pipe shell.

13. The water supply pipes are buried underground. The load on the buried pipe due to earth filling is given by
a) W = C*Y*B
b) W = C*Y/B
c) W = C*Y*B2
d) W = C*Y2*B

View Answer

Answer: c [Reason:] According to Marston, the load W on buried pipes due to earth filling is given by W = C*Y*B2 where, ‘C’ is the coefficient which depends on soil, ‘Y’ is the unit weight of back fill material and ‘B’ is the width of the trench.

14. Which of the following stress in pipe depends on temperature?
a) Internal water pressure
b) Stress due to foundation reaction
c) Longitudinal stress
d) Temperature stress

View Answer

Answer: d [Reason:] Temperature stress is caused in pipes when they are laid above ground. When they are subjected to temperature variation, changes in the length of pipe takes place.

15. Pipe corrosion can be minimized by
a) Removal of copper sulfate
b) Addition of calcium carbonate
c) Addition of carbon dioxide
d) Removal of dissolved oxygen

View Answer

Answer: d [Reason:] Pipe corrosion can be minimized by pH adjustment, control of calcium carbonate, removal of dissolved oxygen, removal of carbon dioxide and by the addition of sodium silicate.

Set 4

1. State whether the following statement is true or false.
The permanent hardness can be removed by adding lime and soda.
a) True
b) False

View Answer

Answer: a [Reason:] The permanent hardness can be removed by adding Ca (OH)2 as lime and sodium carbonate as soda in water and the process is called lime soda process.

2. The time required for the mixing of lime and soda in lime soda process is
a) 10min
b) 20min
c) 40min
d) 80 min

View Answer

Answer: c [Reason:] The time required for the mixing of lime and soda in water in lime soda process is between 30-60min to allow completion of the chemical reaction. Precipitated chemicals are removed by sedimentation or filtration or both.

3. The temperature at which the softening of water takes place by lime soda process is
a) 10o-21oC
b) 20o-30oC
c) 39o-45oC
d) 90oC

View Answer

Answer: a [Reason:] The lime soda process can be operated continuously or intermittently at either 10o-21oC or at 100oC.

4. Which chemical is used for the removing the permanent hardness of Calcium chloride?
a) Lime
b) Chlorine
c) Soda
d) Both lime and soda

View Answer

Answer: b [Reason:] Only soda ash is used for removing the permanent hardness of Calcium chloride whereas for magnesium chloride both lime and soda is used for removing the permanent hardness.

5. Softening chemicals, lime and soda do not depend on
a) Free carbon dioxide present
b) Non carbonate hardness
c) Total magnesium
d) Carbonate hardness

View Answer

Answer: d [Reason:] Lime and soda depend on free carbon dioxide present, non carbonate hardness, total magnesium and does not depend on carbonate hardness.

6. The detention period of a lime soda treatment plant is
a) 1hour
b) 3hours
c) 2-4hours
d) 4-7hours

View Answer

Answer: c [Reason:] The detention period of a lime soda treatment plant is 2-4 hours to obtain greater clarification.

7. The minimum reaction time allowed in the recarbonation basin is
a) 5minutes
b) 10minutes
c) 15minutes
d) 20minutes

View Answer

Answer: d [Reason:] During lime soda treatment, the recarbonation of water is done in recarbonation basin where the minimum reaction time is 20minutes.

8. What is the pH at which recarbonation should be done?
a) 7
b) 4.5
c) 8.2
d) 9.5

View Answer

Answer: d [Reason:] The carbonation of water containing excess lime will form a colloidal precipitate of calcium carbonate that is less soluble at pH 9.4-9.6, so the recarbonation should not be done below this range.

9. Which filter is normally used in the lime soda treatment plant?
a) Slow sand filter
b) Rapid sand filter
c) Dual media filter
d) Mixed media filter

View Answer

Answer: b [Reason:] The recarbonated water in lime soda treatment plant is passed through the rapid filter to ensure complete clarification.

10. What is the detention time of a water softening accelerator?
a) 1-6minutes
b) 20minutes
c) 30 minutes
d) 1-2hours

View Answer

Answer: d [Reason:] A water softening accelerator is a device which is used for mixing, flocculation and clarification of water and they have a short detention period in comparison to sedimentation tank that is 1-2hours.

11. The sludge in water softening accelerator is deposited at
a) Sedimentation tank
b) Reaction zone
c) Concentrator
d) Secondary mixing zone

View Answer

Answer: c [Reason:] The sludge in water softening accelerator is deposited at concentrator which can be discharged through a pipe continuously or can be discharged upon a schedule that can operate automatically.

Set 5

1. Which water treatment process is done after filtration of water?
a) Primary sedimentation
b) Disinfection
c) Secondary sedimentation
d) Flocculation

View Answer

Answer: b [Reason:] Disinfection is a process which is done to kill microorganism present in the water after the filtration process.

2. Which of the following is wrong regarding disinfection?
a) It should be readily available at reasonable cost
b) Its method of application should be simple
c) It should render the water toxic for its intended use
d) It should act as safeguard against re-contamination

View Answer

Answer: c [Reason:] Disinfection should not render the water toxic, objectionable and unpalatable for its intended use.

3. Boiling of water is a _____ method of disinfection.
a) Physical
b) Chemical
c) Mechanical
d) Electrical

View Answer

Answer: a [Reason:] Boiling of water is a physical method of disinfection which is also called as disinfection by heat.

4. Sunlight is a ________ method of disinfection.
a) Physical
b) Chemical
c) Mechanical
d) Electrical

View Answer

Answer: a [Reason:] Sunlight is a natural disinfection. Irradiation by ultraviolet rays promotes disinfection.

5. Which of the following is a chemical method of disinfection?
a) Disinfection by heat
b) Disinfection by light
c) Metal ions
d) Metal ions, Alkalis and acids

View Answer

Answer: d [Reason:] Disinfection by heat and light are physical methods of disinfection whereas metal ions, alkalis and acids are chemical methods of disinfection.

6. The pathogenic bacteria do not last long at a pH ______
a) >11
b) <11
c) <8
d) >8

View Answer

Answer: a [Reason:] The pathogenic get killed at pH>11 which is very alkaline in nature or at pH=3 which is highly acidic.

7. Which minor method of disinfection is effective in complete sterilization of water?
a) Boiling method
b) Excess lime treatment
c) Silver treatment
d) Ultraviolet ray treatment

View Answer

Answer: a [Reason:] Boiling method is effective in complete sterilization of water as it kills all the bacteria and microorganism present in water.

8. What is the dose of lime required in the excess lime treatment?
a) 10-20ppm
b) 0-10ppm
c) 5-10ppm
d) 5-20ppm

View Answer

Answer: a [Reason:] The dose of lime used in the excess lime treatment is 10-20ppm and the excess lime can be removed by the process of re-carbonation.

9. At what pH, the E-Coli bacteria will die in the water?
a) 6
b) 7
c) 9
d) >9.5

View Answer

Answer: d [Reason:] The E-Coli bacteria will die at a pH>9. This can be done with the help of excess lime treatment.

10. The depth of water while using ultra violet ray treatment for disinfection should be ____
a) 35cm
b) 46cm
c) 28cm
d) 10cm

View Answer

Answer: d [Reason:] The depth of water while using ultra violet ray treatment for disinfection should not exceed 10 cm and its turbidity should be in the range of 15-20ppm.

11. Which method of disinfection is mainly used in rural areas?
a) Boiling method
b) Excess lime treatment
c) Potassium permanganate treatment
d) Silver treatment

View Answer

Answer: c [Reason:] The Potassium permanganate treatment is used in rural areas where most of the water is drawn from a well which contains the least amount of bacteria.

12 The dose of KMnO4 required for disinfection of water is _______ ppm
a) 1-2
b) 2-3
c) 3-4
d) 4-7

View Answer

Answer: a [Reason:] The normal dose of KMnO4 required for disinfection of water varies between 1 to 2ppm with a contact period of 4 to 6 hours.

13. Addition of KMnO4 to water imparts _____ color.
a) Blue
b) Red
c) Pink
d) White

View Answer

Answer: c [Reason:] Addition of KMnO4 to water imparts pink color. It not only kills the bacteria, but also helps in oxidizing the taste producing organic matter.

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