Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca(OH)2. It is a colorless crystal or white powder and is obtained when calcium oxide (called lime or quicklime) is mixed, or slaked with water. It has many names including hydrated lime, builders lime, slack lime, cal, or pickling lime. Calcium hydroxide is used in many applications, including food preparation. Limewater is the common name for a saturated solution of calcium hydroxide. When heated to 512 °C, the partial pressure of water in equilibrium with calcium hydroxide reaches 101 kPa, which decomposes calcium hydroxide into calcium oxide and water.[3] Ca(OH)2 → CaO + H2O A suspension of fine calcium hydroxide particles in water is called milk of lime. The solution is called limewater and is a medium strength base that reacts with acids and attacks many metals. Limewater turns milky in the presence of carbon dioxide due to formation of calcium carbonate, a process called carbonatation: Ca(OH)2 + CO2 → CaCO3 + H2O Calcium hydroxide adopts a polymeric structure, as do the related hydroxides of the alkaline earth metals. The packing resembles the cadmium iodide motif with layers of octahedral Ca centres. Strong hydrogen bonds exist between the layers. Calcium hydroxide is produced commercially by treating lime with water: CaO + H2O → Ca(OH)2 In the laboratory it can be prepared by mixing aqueous solutions of calcium chloride and sodium hydroxide. The mineral form, portlandite, is relatively rare but can be found in some volcanic, plutonic, and metamorphic rocks. It has also been known to arise in burning coal dumps.
Posted on: Sun, 10 Aug 2014 02:40:04 +0000
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