The disinfectant used in municipal water supply that provides residual protection is: MCQ with Answer and Explanation

Question
The disinfectant used in municipal water supply that provides residual protection is:
A. Boiling
B. Ozone
C. Chlorine
D. UV radiation
Answer: Option C
Solution (By JKExamLibrary)
Chlorine leaves a residual in water, continuing to protect against recontamination in distribution pipes. Ozone and UV kill instantly but do not provide residual disinfection. Boiling is not used for municipal supply.
This question belongs to: Science chemistry

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Practice More chemistry Questions

Question #1
The acid present in ant sting is:
A. Acetic acid
B. Lactic acid
C. Formic acid
D. Citric acid
Discuss

Correct Answer: Option C

Explanation:
Ant sting contains formic acid (methanoic acid, HCOOH), causing irritation. Nettle sting also contains formic acid. To neutralize, apply a base like baking soda. Acetic acid is in vinegar, citric acid in citrus fruits, lactic acid in sour milk and muscles. Formic acid is the simplest carboxylic acid.
This question belongs to: Science chemistry
Question #2
Which of the following is an example of oxidation?
A. Cu²⁺ + 2e⁻ → Cu
B. Cl₂ + 2e⁻ → 2Cl⁻
C. 2H⁺ + 2e⁻ → H₂
D. Na → Na⁺ + e⁻
Discuss

Correct Answer: Option D

Explanation:
Oxidation is loss of electrons. Na loses an electron to become Na⁺, so it is oxidized. Options A, C, D involve gain of electrons (reduction). Oxidation also can be defined as gain of oxygen or loss of hydrogen. In the reaction, Na acts as reducing agent. Mnemonic: LEO (Loss of Electrons is Oxidation) GER (Gain of Electrons is Reduction).
This question belongs to: Science chemistry
Question #3
Which salt causes permanent hardness?
A. Mg(HCO₃)₂
B. CaSO₄
C. Na₂CO₃
D. Ca(HCO₃)₂
Discuss

Correct Answer: Option B

Explanation:
Calcium sulfate and magnesium sulfate/chloride cause permanent hardness. Bicarbonates cause temporary hardness removable by boiling.
This question belongs to: Science chemistry
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