Hardness of Water MCQs Quiz Multiple Choice Questions & Answers

1. A water sample found to possess 16.2 mg/L of Ca(HCO₃)₂. Its hardness in terms of CaCO₃ equivalents is

1. 100
2. 10
3. 16.2
4. 1000

2. Biological oxidation processes usually referred as biological treatment, are the most common form of

1. Primary treatment
2. secondary treatment
3. Tertiary treatment
4. all of the above

3. Blow – down operation cause the removal of

1. Scales
2. sludges
3. acidity
4. sodium chloride

4. Boiler corrosion caused by using high alkaline water in a boiler is called

1. Corrosion
2. boiler corrosion
3. caustic embrittlement
4. erosion

5. Brackish water mainly contains

1. Calcium salts
2. Magnesium salts
3. Turbidity
4. sodium chloride

6. Calgon is the trade name given to

1. Sodium silicate
2. Sodium hexa meta phosphate
3. Sodium meta phosphate
4. Calcium phosphate

7. Calgon is used for the removal of

1. Sodium carbonate
2. permanent hardness of water
3. Hardness of water
4. none of these

8. Caustic embrittlement can be avoided by using

1. Sodium phosphate
2. hydrogen
3. ammonium hydroxide
4. sodium sulphate

9. Caustic embrittlement is a type of

1. Boiler corrosion
2. conditioning
3. scale formation
4. sludge formation.

10. Disinfection by ozone is due to liberation of

1. Oxygen
2. nascent Oxygen
3. Molecular Oxygen
4. oxide

11. Estimation of hardness of water by EDTA method is used to determine

1. Alkaline hardness
2. temporary hardness only
3. Permanent hardness only
4. all the above

12. Hard water can be softened by passing it through

1. Lime stone
2. sodium hexa meta phosphate
3. Ion – exchange resin
4. sodium silicate

13. Hard water is unfit for use in boilers for generating steam because

1. Its boiling point is high
2. Hard water does not produce lather inside boiler
3. Water decomposes into O2 and H2
4. It produces scales inside the boiler

14. Hardness in water is caused due to the presence of

1. Undissolved salts of Ca²⁺ and Mg²⁺
2. Dissolved sulfates of Potassium
3. Dissolved salts of Ca²⁺ and Mg²⁺
4. Undissolved CaCO₃

15. Hardness of water does not

1. Have any bad effect in boiler
2. make cooking of food difficult
3. Make it unfit for drinking
4. cause difficulty in washing clothes with soaps.

16. Hardness of water is expressed in equivalents of

1. CaCO₃
2. MgCO₃
3. Ca(HCO₃)₂
4. Mg(HCO³)²

17. Hardness of water is measured in

1. Degree Clarke
2. ppm
3. degree French
4. mg /L

18. Liquid chlorine is a most effective

1. Disinfectant
2. coagulant
3. floculant
4. sterilizing agent

19. One of the following chemical acts as both coagulant and softening agent

1. Lime
2. soda
3. soda
4. sodium aluminate

20. One of the following is an example for cation exchanging resin

1. Copolymer of phenol formaldehyde – amine formaldehyde
2. Copolymer of styrene – divinyl benzene
3. Copolymer of phenol formaldehyde and styrene
4. Copolymer of amine formaldehyde and divinely benzene

21. One part of CaCO₃ equivalent hardness per 10⁵ parts of water is called

1. Degree Clarke
2. ppm
3. degree French
4. mg /L

22. Permanent hardness in water is caused by the presence of

1. Bicarbonates of calcium and magnesium
2. Carbonates of sodium and potassium
3. Chlorides of sulfates and calcium and magnesium
4. Phosphates of sodium and potassium

23. Solubility of calcium sulphate in water is

1. Increase with rise of temperature
2. Decreases with rise of temperature
3. Remains unaltered with rise of temperature
4. Does not adopt any definite pattern with rise of temperature.

24. Temporary hardness in water is removed by

1. Filtration
2. Sedimentation
3. Boiling
4. coagulation.

25. Temporary hardness of water is caused by the presence of

1. Chlorides of calcium and magnesium
2. Sulfates of calcium and magnesium
3. Bicarbonates of calcium and magnesium
4. Carbonates of calcium and magnesium.

26. The common methods used for disinfection in waste water treatment plants are

1. Chlorination
2. UV light
3. Both a & b
4. Phenolic solvent

27. The external treatment of boiler feed water is done by

1. Lime – soda process
2. sodium sulphate treatment
3. Calgon process
4. sodium aluminate treatment.

28. The formula of chloramine is

1. ClNH₂
2. NHCl₂
3. NCl₃
4. NH₂Cl₂

29. The hardness of water in CaCO₃ equivalents containing MgSO₄ (Mol. Wt = 120) with concentration of 12 mg/ L is

1. 100 mg/L
2. 10 mg/L
3. 5 mg/L
4. 1 mg/L

30. The hardness of water sample is 10 ppm, which can be expressed as.............degree Clarke.

1. 0.3
2. 0.4
3. 0.5
4. 0.7

31. The ion – exchange resins used for softening water are

1. Cross linked polymers with micro porous structure
2. Branched polymers with porous structure
3. Cross linked polymers with non-porous structure
4. Branched polymers with non – porous structure

32. The maximum desirable limits (as per BIS) of total hardness (as CaCO₃) in drinking water is

1. 600 ppm
2. 300 ppm
3. 500 ppm
4. 1000 ppm

33. The method by which ions are pulled out of salt water by direct current, and employing thin and rigid membrane is called

1. Electrodialysis
2. reverse osmosis
3. Zeolite
4. ion exchange

34. The process of allowing water to stand undisturbed in big tanks for settling of the suspended particles due to force of gravity

1. Coagulation
2. conditioning
3. sedimentation
4. screening

35. The process of wet steam formation is called

1. Foaming
2. priming
3. corrosion
4. caustic embrittlement.

36. The purification of brackish water y reverse osmosis is also called as

1. Super – filtration
2. Supra – filtration
3. Hypo – filtration
4. filtration

37. The soft, loose and slimy precipitate formed within the boiler is called

1. Scale
2. sludge
3. embrittlement
4. coagulation

38. Ultraviolet rays are used in the treatment of water for

1. Filtration
2. Sedimentation
3. Screening
4. Sterilization.

39. Uneven deposition of turbines causes

1. Vibrational problems
2. Heat problems
3. Power problems
4. Uncontrolled cooling.

40. When temporary hard water is boiled, one of the substance formed is

1. CaCO₃
2. CaSO₄
3. HCl
4. CO₂

41. Which of the following chemical is sometimes added in the process of coagulation and flocculation.

1. Aluminum sulphate
2. Aluminium oxide
3. Calcium chloride
4. none of these

42. Which of the following methods separates ionic and non – ionic impurities from water?

1. Electrodialysis
2. deionization
3. reverse osmosis
4. zeolite process

43. Which of the following physical method is used as germicidal in modern time for the treatment of drinking water?

1. Chlorination
2. Treating with Potassium permanganate
3. UV radiation
4. Treating with Bleaching powder

44. Which of the following salts cause least hardness to water when converted to CaCO₃ equivalents?

1. 10 mg of CaCO₃
2. 19 mg of CaSO₄
3. 10 mg of MgCl₂
4. 10 mg of CaCl₂

45. Which of the following substances are commonly used in a filter?

1. Charcoal
2. Sand
3. both a & b
4. Aluminium Chloride

46. Zeolite softening process removes

1. Only temporary hardness of water
2. Only permanent hardness of water
3. Both temporary and permanent hardness of water
4. The dissolved gases in permanent hard water.

47. Zeolite used in zeolite softening process for the treatment of hard water gets exhausted after certain time of usage but can be regenerated by flushing it with

1. 10% calcium chloride solution
2. 10% Magnesium Chloride solution
3. 10% Magnesium sulphate solution
4. 10% sodium chloride solution