Question

Bleaching powder is obtained by the action of chlorine gas and

• A. dilute solution of $Ca(OH)_2$
• B. concentrated solution of $Ca(OH)_2$
• C. dry CaO
• D. dry slaked lime

Answer 1

The Correct Option is D

Bleaching powder, chemically known as calcium hypochlorite, is commonly used for bleaching and disinfection purposes. The process of manufacturing bleaching powder involves a reaction between chlorine gas and dry slaked lime.

1. Chemical Reaction: The chemical reaction for the formation of bleaching powder is:
   2Ca(OH)_2 + 2Cl_2 \rightarrow Ca(OCl)_2 + CaCl_2 + 2H_2O
   Here, Ca(OCl)_2 is the bleaching powder, and Ca(OH)_2 is the slaked lime.
2. Explanation of Options:
   • Option 1: Dilute solution of Ca(OH)_2 - A dilute solution of slaked lime is not effective for the formation of bleaching powder as the water content interferes with the chlorine reaction.
   • Option 2: Concentrated solution of Ca(OH)_2 - Despite being concentrated, the presence of water in any solution form would still hinder effective bleaching powder formation, as moisture would react differently with chlorine.
   • Option 3: Dry CaO - Calcium oxide or quicklime doesn't react directly with chlorine gas under normal conditions to yield bleaching powder.
   • Option 4: Dry slaked lime - This is the correct option, as dry slaked lime provides the solid surface necessary for the reaction with chlorine gas, producing bleaching powder.
3. Conclusion: Thus, the correct answer is dry slaked lime, as it allows the formation of bleaching powder through a direct reaction with chlorine gas.