Which is used for sterilization of water in water supply system of cities?

Options

A. Chlorine
B. Sulphurdioxide
C. Potassium permanganate
D. DDT

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks which chemical is used for the sterilization of water in the water supply systems of cities. This involves identifying a disinfectant that can effectively eliminate microorganisms from water.

2. **Defining Sterilization of Water**: Sterilization of water is a process that aims to kill, eliminate, and deactivate all forms of microorganisms present in the water. This is crucial for ensuring that the water is safe for consumption and free from waterborne diseases.

3. **Identifying Common Disinfectants**: There are several chemicals that are commonly used for water sterilization. The primary disinfectants include:
- Chlorine
- Chlorine dioxide
- Ozone

4. **Focusing on Chlorine**: Among these disinfectants, chlorine is the most widely used in municipal water supply systems. It is effective in killing pathogens such as bacteria and viruses.

5. **Mechanism of Action**: Chlorine works by breaking the chemical bonds in the molecules of pathogens. This disrupts their structure and function, leading to their inactivation. The relevant chemical species involved in this process include hypochlorous acid (HOCl) and hypochlorite ions (OCl⁻), which release free chlorine that acts as a disinfectant.

6. **Conclusion**: Based on the effectiveness and widespread use of chlorine in water treatment processes, the correct answer to the question is chlorine.

**Final Answer**: Chlorine is used for sterilization of water in the water supply system of cities.

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