SSC Selection Post 2025 PYQ — Question 6

Correct Answer

Disinfecting drinking water

Explanation

Bleaching powder, chemically known as calcium oxychloride (CaOCl_2), is widely used as a disinfectant to sanitize and decontaminate drinking water. When bleaching powder is dissolved in water, it releases chlorine gas (Cl_2), which reacts with water to form hypochlorous acid (HOCl). This active compound acts as a powerful oxidizing agent that effectively kills harmful microorganisms, bacteria, and pathogens present in water, making it safe for human consumption.

Beyond its primary function as a bleaching agent in textile and paper industries, it serves as a critical agent in public health sanitation, swimming pool maintenance, and as an oxidizing agent in various chemical laboratory synthesis processes.

Key Points

Bleaching powder is synthesized by passing chlorine gas over dry slaked lime, represented by the chemical equation

Ca(OH)_2 + Cl_2 → CaOCl_2 + H_2O

. It is classified as an inorganic compound that readily loses its chlorine content when exposed to air over long periods. In addition to water purification, it is used in manufacturing chloroform (CHCl_3) and rendering wool unshrinkable.

Important Questions and Answers

Question: What is the exact chemical name and formula of commercial bleaching powder?

Answer: Calcium oxychloride, represented as CaOCl2.

Question: Which active gas is released when bleaching powder reacts with dilute acids, giving it its characteristic strong odor?

Answer: Chlorine gas (Cl2).