Hard water contains dissolved: MCQ with Answer and Explanation

Hard water contains dissolved:
A. Potassium salts
B. Ammonium salts
C. Sodium salts
D. Calcium and magnesium salts
Answer: Option D
Solution (By JKExamLibrary)
Hardness is caused by Ca²⁺ and Mg²⁺ ions in the form of bicarbonates, sulfates, chlorides. They react with soap to form scum.

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Practice More chemistry Questions

Question #1
Which of the following is an unsaturated hydrocarbon?
A. Methane
B. Cyclohexane
C. Propane
D. Benzene

Correct Answer: Option D


Explanation:
Unsaturated hydrocarbons contain at least one double or triple bond between carbon atoms. Benzene (C6H6) has a ring structure with alternating double bonds (delocalized pi electrons), making it highly unsaturated. Cyclohexane, propane, and methane contain only single bonds and are saturated hydrocarbons.

This question belongs to: Science chemistry
Question #2
Which of the following is NOT a characteristic of an ideal gas?
A. No intermolecular forces
B. Obeys PV = nRT at all conditions
C. Particles have no volume
D. Particles have strong attractive forces

Correct Answer: Option D


Explanation:
Ideal gas assumptions: particles have negligible volume, no intermolecular forces, and elastic collisions. Real gases deviate due to finite molecular size and attractions. At high pressure and low temperature, real gases deviate significantly; van der Waals equation corrects. So having strong attractive forces is not an ideal gas property. Ideal gas law PV = nRT is a limiting law.

This question belongs to: Science chemistry
Question #3
Ozonation of water is preferred over chlorination because:
A. It removes hardness.
B. It is easier to transport.
C. It is cheaper.
D. It does not leave any harmful residual taste or toxic byproducts.

Correct Answer: Option D


Explanation:
Ozonation is a powerful disinfection method that kills bacteria and viruses faster than chlorine. Unlike chlorine, ozone decomposes back into oxygen and does not leave a residual taste or form harmful chlorinated organic byproducts (like trihalomethanes), making it safer for drinking water.

This question belongs to: Science chemistry