Understanding Chlorine Gas and its Uses

The question asks about the use of chlorine gas in the manufacture of common substances listed in the options. Chlorine (\(\text{Cl}_2\)) is a highly reactive nonmetal, commonly used in various industrial processes due to its strong oxidizing and bleaching properties.

Manufacture of Bleaching Powder

Bleaching powder, also known as calcium oxychloride (\(\text{CaOCl}_2\)), is a chemical compound widely used as a bleaching agent and disinfectant. Its manufacture involves the reaction of chlorine gas with dry slaked lime.

Dry slaked lime is calcium hydroxide, represented by the chemical formula \(\text{Ca(OH)}_2\). When chlorine gas is passed over dry slaked lime, bleaching powder is formed along with water. This process is the primary method for producing bleaching powder commercially.

The chemical reaction for the manufacture of bleaching powder is:

\(\text{Ca(OH)}_2\text{(s)} + \text{Cl}_2\text{(g)} \rightarrow \text{CaOCl}_2\text{(s)} + \text{H}_2\text{O(l)}\)

Here:

• \(\text{Ca(OH)}_2\) is dry slaked lime.
• \(\text{Cl}_2\) is chlorine gas.
• \(\text{CaOCl}_2\) is bleaching powder.
• \(\text{H}_2\text{O}\) is water.

This reaction clearly shows that chlorine gas is a key reactant in the manufacturing process of bleaching powder.

Why Not Other Options?

Let's briefly look at the main ingredients and processes for the other options to understand why chlorine gas is not typically used in their manufacture:

• Baking Powder: Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate (like sodium bicarbonate, \(\text{NaHCO}_3\)) and a weak acid (like cream of tartar). Its production does not involve chlorine gas.
• Baking Soda: Baking soda is sodium bicarbonate (\(\text{NaHCO}_3\)). It is primarily manufactured using the Solvay process, which uses sodium chloride, ammonia, carbon dioxide, and calcium carbonate. Chlorine gas is not used in this process. (Note: Sodium chloride, used in Solvay process, can be obtained from electrolysis which produces chlorine as a byproduct, but chlorine is not a direct reactant for making baking soda).
• Washing Powder: Washing powder (laundry detergent) is a complex mixture containing surfactants, builders (like sodium carbonate or zeolites), enzymes, and other additives. While some components might involve processes where chlorine is indirectly related (e.g., production of some chemicals), chlorine gas itself is not a direct ingredient in the primary manufacturing process of the bulk product like sodium carbonate or surfactants used in washing powder.

Based on the manufacturing processes, chlorine gas is directly used as a reactant in the production of bleaching powder.

Revision Table: Common Chemicals and Manufacture Inputs

Additional Information: Properties of Chlorine Gas

Chlorine is a greenish-yellow gas with a pungent, irritating odor. It is denser than air and is toxic. Its uses are diverse, including:

• Disinfection of water supplies and swimming pools.
• Manufacture of plastics like PVC (polyvinyl chloride).
• Production of various chemicals, including solvents, pesticides, and pharmaceuticals.
• Bleaching of pulp and textiles (though its use in some areas is decreasing).

The reaction with slaked lime to produce bleaching powder is one significant industrial application leveraging its reactive nature.