The disinfecting action of chlorine during chlorination is mainly due to the action of: September 2011
**Core Concept**
The disinfecting action of chlorine is a crucial aspect of water treatment, relying on the generation of **hypochlorous acid (HOCl)**, which is the primary disinfectant. Chlorine's effectiveness stems from its ability to denature proteins and disrupt cell membranes in microorganisms. This process is fundamental in **water purification** and **public health**.
**Why the Correct Answer is Right**
The correct answer is related to the formation of **hypochlorous acid (HOCl)**, which is the most effective form of chlorine for disinfection. When chlorine is added to water, it reacts with water to form **hypochlorous acid (HOCl)** and **hydrochloric acid (HCl)**. **Hypochlorous acid (HOCl)** then acts as a strong disinfectant by damaging the cell walls of microorganisms, ultimately leading to their death. This mechanism underlies the use of chlorine in **water treatment** and **disinfection protocols**.
**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because, while **hydrochloric acid (HCl)** is formed during the reaction of chlorine with water, it does not have significant disinfectant properties compared to **hypochlorous acid (HOCl)**.
**Option B:** Incorrect, as the direct action of **chlorine gas** itself is not the primary mechanism of disinfection in water treatment.
**Option D:** This option is also incorrect because, although **chlorine** is the initial substance added for disinfection, its effectiveness is mainly through the formation of **hypochlorous acid (HOCl)**.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the effectiveness of chlorine as a disinfectant is highly dependent on the **pH of the water**, with **hypochlorous acid (HOCl)** being more dominant and effective at lower pH levels. This knowledge is crucial for **public health** and **environmental health** practices.
**Correct Answer:** Correct Answer: B. Hypochlorous acid.