Which of the following can be used for purification of water? ​

Correct option is A

Correct Answer: Alum

Explanation:
Alum, chemically known as potassium aluminum sulfate, is extensively used for water purification. Its primary function is as a coagulant, which helps in removing suspended particles and impurities from water. When alum is added to water, it reacts to form a gel-like precipitate that traps fine particles, organic matter, and microorganisms. This process is called flocculation. Once the floc (clumped impurities) settles, the water becomes clearer and safer for use.

Key Points:

• Coagulation Property: Alum promotes flocculation, which aggregates suspended particles into larger clumps.
  
• Removes Turbidity: It significantly reduces water turbidity by settling suspended particles.
  
• Microorganism Reduction: The coagulation process traps harmful microorganisms, making water safer.
  
• Widely Used: Alum is used in municipal water treatment plants and household water purification systems.
  
• Safe in Moderation: Alum should be used in appropriate amounts to avoid excess chemical residue in water.

Other Options:

• Sodium: Highly reactive metal; not suitable for water purification as it reacts vigorously with water, producing hydrogen gas and heat.
• Nitrogen: An inert gas; does not have properties for coagulating or purifying water.
• Carbon Dioxide: Primarily used in carbonation processes for beverages, not effective for water purification.