Water Hardness MCQs

By: Prof. Dr. Fazal Rehman | Last updated: May 29, 2025

1. : __________ is the end point of the titration in the soap titration method.
(A) Formation of lather
(B) Formation of salts
(C) Formation of carbonates
(D) Formation of bicarbonates

2. : All the hardness causing ions can be precipitated into their respective _____ by the sodium soap.
(A) Carbonates
(B) Bicarbonates
(C) Stereates
(D) Chlorides

3. : _________ is the water that forms lather directly with the soap.
(A) Hard water
(B) Soft water
(C) Partially hard water
(D) Very hard water

4. : By titrating the fixed volume of water against the standard __________ solution we can determine the total hardness of the water.
(A) Soap
(B) Alkaline soap
(C) Acidic soap
(D) Alcoholic soap

5. : __________ is the indicator used in the EDTA method.
(A) Benzene
(B) Phenolphthalein
(C) Ethylene diamine
(D) Eriochrome Black T

6. : ___________ is the hardness a soft water contains.
(A) 0-45 ppm
(B) 0-55 ppm
(C) 0-65 ppm
(D) 0-75 ppm

7. : ________ is also called EDTA method.
(A) Complexometric titration
(B) Complex titration
(C) Complement titration
(D) Complexion titration

8. : By the ___ types estimation of the hardness of water can be determined.
(A) 2
(B) 3
(C) 4
(D) 5

9. : To form ________ with metal ions EDTA has the ability.
(A) Stable complexes
(B) Unstable complexes
(C) Salts
(D) Acids

10. : The metal-dye complex has the _______ color at pH 10.
(A) Wine red
(B) Blue
(C) Green
(D) Pink

11. : ________ grams of EDTA is dissolved in one litre of water to prepare EDTA solution.
(A) 1
(B) 2
(C) 3
(D) 4

12. : The standard hard water is prepared to ensure that each mL must contain _______ mg of CaCO₃.
(A) 1
(B) 2
(C) 3
(D) 4

13. : The moderately hard water contains the hardness of ____________.
(A) 75-150 ppm
(B) 75-120 ppm
(C) 75-130 ppm
(D) 75-100 ppm

14. : Dye and dye-metal complex have the __________ colour.
(A) Same
(B) Different
(C) Same in only some cases
(D) Cannot be known

15. : The formula of total hardness can be given by ________.
(A) Temporary + permanent hardness
(B) Temporary – permanent hardness
(C) Temporary × permanent hardness
(D) Temporary ÷ permanent hardness

16. : In the EDTA method, ________ drops of the indicator is used.
(A) 1 to 2 drops
(B) 2 to 3 drops
(C) 2 to 4 drops
(D) 5 to 8 drops

17. : pH of __________ must be present in the EDTA solution in the buffer used.
(A) 20
(B) 15
(C) 10
(D) 5

18. : At the pH of _______ the change in color is sharper.
(A) 5
(B) 10
(C) 15
(D) 20

19. : CaCO₃ is given by __________ for the very hard water’s hardness.
(A) 100–200 ppm
(B) 100–300 ppm
(C) 200–300 ppm
(D) Above 300 ppm

20. : Drinking water has the ________ pH value.
(A) 6.5–8.5
(B) 5.5–6.5
(C) 4.5–5.5
(D) 3.5–4.5

21. : The amount of iron in drinking water can range about______
(A) 1–1.5 ppm
(B) 0.01–0.1 ppm
(C) 1–1.1 ppm
(D) 0.1–1 ppm

22. : The amount of phosphate in drinking water can have the range of ______
(A) 5–10 ppm
(B) 10–15 ppm
(C) 15–20 ppm
(D) 20–25 ppm

23. : The amount of organic matter in drinking water must be ______
(A) 0.2–1.0 ppm
(B) 1.0–2.0 ppm
(C) 2.0–3.0 ppm
(D) 3.0–4.0 ppm

24. : Soluble salts turn into insoluble salts when the water is heated during the filtration in ______ and removed after filtration.
(A) Temporary hardness
(B) Permanent hardness
(C) Non-carbonate
(D) Non-alkaline

25. : Magnesium limit in drinking water is about ___________
(A) 10–150 ppm
(B) 20–150 ppm
(C) 30–150 ppm
(D) 40–150 ppm

26. : The amount of chloride in the drinking water range can be about __________
(A) 200–600 ppm
(B) 300–600 ppm
(C) 400–600 ppm
(D) 500–600 ppm

27. : Permanent hardness in water does not produce the_____________
(A) Nitrates
(B) Sulphates
(C) Chlorides
(D) Bicarbonates

28. : Select the process that does not remove the permanent hardness of water?
(A) Lime-soda
(B) Ion exchange process
(C) Zeolite process
(D) Heating

29. : Choose one of the following options: Carbonate and bicarbonates are
(A) Alkaline
(B) Acidic
(C) Highly acidic
(D) Neutral