Question

Bleaching powder is obtained by passing chlorine over :

• A. Sodium
• B. Lime stone
• C. Gypsum
• D. Slaked lime

Hint:

Bleaching powder (\(\text{CaOCl}_2\)) production involves: {Chlorine gas (\(\text{Cl}_2\))} + {Slaked Lime (\(\text{Ca(OH)}_2\))} \(\rightarrow\) Bleaching Powder + Water Remember these key reactants:
Slaked lime = Calcium Hydroxide = \(\text{Ca(OH)}_2\)
Quick lime = Calcium Oxide = CaO (Slaked lime is made from quick lime + water)
Lime stone = Calcium Carbonate = \(\text{CaCO}_3\) The reactant with chlorine is slaked lime.

Answer 1

The Correct Option is D

Concept: Bleaching powder is a chemical compound with bleaching properties, commonly used as a disinfectant and for whitening fabrics. Its chemical name is calcium oxychloride or calcium hypochlorite (though its actual composition is complex, often represented as \(\text{Ca(OCl)Cl}\) or \(\text{CaOCl}_2\)). Step 1: The Manufacturing Process of Bleaching Powder Bleaching powder is manufactured by the reaction of chlorine gas (\(\text{Cl}_2\)) with dry slaked lime (\(\text{Ca(OH)}_2\)). The chemical equation for this reaction is: \[ \text{Ca(OH)}_2(s) + \text{Cl}_2(g) \rightarrow \text{CaOCl}_2(s) + \text{H}_2\text{O}(l) \] Slaked lime is calcium hydroxide. Step 2: Analyzing the options
(1) Sodium (\(\text{Na}\)): Sodium is a highly reactive metal. Chlorine reacts with sodium to form sodium chloride (NaCl, common salt), not bleaching powder.
(2) Lime stone (\(\text{CaCO}_3\)): Limestone is calcium carbonate. Chlorine gas does not readily react with calcium carbonate under normal conditions to produce bleaching powder. Calcium carbonate is used to produce quicklime (CaO) by heating, which is then hydrated to form slaked lime.
(3) Gypsum (\(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\)): Gypsum is calcium sulfate dihydrate. It is not used in the direct production of bleaching powder with chlorine.
(4) Slaked lime (\(\text{Ca(OH)_2\)):} Correct. Passing chlorine gas over dry slaked lime (calcium hydroxide) is the standard industrial method for producing bleaching powder. Therefore, bleaching powder is obtained by passing chlorine over slaked lime.