Ozone is used to purify water because it: MCQ with Answer and Explanation

Ozone is used to purify water because it:
A. Adds odor
B. Makes water acidic
C. Adds minerals
D. Is a strong disinfectant and leaves no harmful residue
Answer: Option D
Solution (By JKExamLibrary)
Ozone (O₃) is a more powerful oxidant than chlorine; it destroys bacteria, viruses, and organic contaminants, and then decomposes to oxygen, leaving no residual taste or toxic disinfection by-products. However, it does not provide lasting protection in distribution pipes, so a small chlorine dose may be added. Ozonation also removes color and odor.

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Which of the following is an endothermic reaction?
A. Respiration
B. Reaction of sodium with water
C. Decomposition of calcium carbonate
D. Burning of natural gas

Correct Answer: Option C


Explanation:
Endothermic reactions absorb heat from the surroundings. The decomposition of calcium carbonate (CaCO₃ → CaO + CO₂) requires continuous heating to proceed. Burning of gas, respiration, and the reaction of sodium with water are all exothermic reactions that release significant amounts of heat energy to the surroundings.

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Which of the following is a mixed fertilizer?
A. Urea
B. Superphosphate
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Correct Answer: Option C


Explanation:
NPK is a mixed (complex) fertilizer containing nitrogen, phosphorus, and potassium. Urea is a straight nitrogenous fertilizer. Ammonium sulfate is nitrogenous. Superphosphate is phosphatic. Mixed fertilizers supply two or more primary nutrients. They can be granulated or blended. DAP provides N and P, but NPK provides all three.

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Which of the following is a compound?
A. Oxygen
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Correct Answer: Option B


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