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प्रश्न
Distinguish between calcination and roasting. Illustrate your answer with examples.
फरक स्पष्ट करा
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उत्तर
| Calcination | Roasting | |
| Definition: | Heating concentrated ore below its melting point in limited air supply. | Heating ore strongly in presence of excess air. |
| Purpose: | Removes moisture, volatile impurities, decomposes carbonates to oxides. | Removes moisture, volatile impurities, and oxidizes sulphides to oxides. |
| Typical Ores: | Carbonate ores (e.g., CaCO3, MgCO3). | Sulphide ores (e.g., CuFeS2, PbS). |
| Chemical Changes: | Carbonates decompose releasing CO2; hydrated oxides lose water. | Sulphides convert to oxides releasing SO2 and other volatile oxides. |
| Example: | \[\ce{CaCO3 -> CaO + CO2}\] (Limestone) | \[\ce{2PbS + 3O2 -> 2PbO + 2SO2}\] (Galena) |
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