In everyday chemistry, what is the common name of the compound calcium oxychloride, CaOCl2?

Introduction / Context:
This question tests your knowledge of common names of important industrial and household chemicals. Many compounds are better known by their everyday names than by their systematic chemical names. Calcium oxychloride, CaOCl2, is widely used as a disinfectant and bleaching agent, especially for bleaching fabrics and disinfection of drinking water. Recognising its common name is a standard exam question in basic chemistry.

Given Data / Assumptions:

• The chemical formula given is CaOCl2, calcium oxychloride.
• Options include baking powder, baking soda, bleaching powder, washing soda and lime powder.
• Each name corresponds to a different well known household or industrial chemical.
• We assume familiarity with basic uses of these compounds.

Concept / Approach:
Bleaching powder is the common name for calcium oxychloride, CaOCl2. It is produced by passing chlorine gas over dry slaked lime (calcium hydroxide). Bleaching powder is used to bleach cotton and linen in the textile industry and to disinfect drinking water and sewage due to its ability to release chlorine. Baking soda is sodium bicarbonate, NaHCO3; baking powder is a mixture containing sodium bicarbonate and acid salts; washing soda is sodium carbonate decahydrate, Na2CO3·10H2O; and lime usually refers to calcium oxide or calcium hydroxide. These are different compounds with different formulas and uses.

Step-by-Step Solution:
Step 1: Recall that bleaching powder is chemically calcium oxychloride and is represented approximately by the formula CaOCl2. Step 2: Bleaching powder is manufactured by passing chlorine gas over dry slaked lime, which is calcium hydroxide, Ca(OH)2. Step 3: It is widely used for bleaching fabrics and wood pulp and for disinfecting water because it slowly releases chlorine. Step 4: Baking soda is NaHCO3, sodium bicarbonate, used in baking and as an antacid, not the same as CaOCl2. Step 5: Baking powder is a mixture containing baking soda and an acid salt, again unrelated to calcium oxychloride. Step 6: Washing soda is Na2CO3·10H2O, sodium carbonate decahydrate, used in cleaning and softening water. Step 7: Lime powder usually refers to CaO or Ca(OH)2, not to CaOCl2. Thus, the correct common name for CaOCl2 is bleaching powder.

Verification / Alternative check:
You can verify this association by remembering typical exam tables: Bleaching powder (CaOCl2 or more exactly Ca(OCl)Cl·H2O), Washing soda (Na2CO3·10H2O), Baking soda (NaHCO3), Baking powder (mixture based on NaHCO3) and Plaster of Paris (CaSO4·1/2H2O). Bleaching powder is always listed as a chlorine releasing disinfectant and bleaching agent. Its application in municipal water disinfection, particularly in rural or emergency situations, is widely discussed. None of the other names match the formula CaOCl2 in standard chemical lists.

Why Other Options Are Wrong:
Baking powder is a mixture, not a single compound, and its key component is sodium bicarbonate, not calcium oxychloride. Baking soda is specifically NaHCO3, with a very different composition and use. Washing soda is sodium carbonate decahydrate, a water softener and cleaning agent, not a disinfectant like bleaching powder. Lime powder refers to calcium oxide or calcium hydroxide and does not contain chlorine. Hence these options do not correspond to the formula CaOCl2 and are incorrect for this question.

Common Pitfalls:
Students sometimes confuse the names baking powder and baking soda, or mix up washing soda and bleaching powder because both are white powders used in household contexts. To avoid such confusion, it helps to associate each compound with its formula and main use: bleaching powder (CaOCl2) for bleaching and disinfection; washing soda (Na2CO3·10H2O) for laundry and water softening; baking soda (NaHCO3) for baking and digestion; and baking powder as a mixture that releases CO2 when heated. Keeping a small table of these common names and formulas in mind can prevent mistakes in multiple choice questions.

Final Answer:
The common name of CaOCl2 (calcium oxychloride) is bleaching powder.