Hardness of Water MCQ Questions and Answers for Practice

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.