Calcium Hydroxide (Slaked lime)
Preparation:
It is prepared by the action of water on quick time.
CaO + H2O → Ca(OH)2
Properties:
(1) White amorphous solid.
(2) It absorbs CO2 gas to form a white ppt of calcium carbonate which becomes colourless when excess of CO2 is passed.
Ca(OH)2 + CO2 → CaCO3 + H2O
CaCO3 + H2O + CO2 → Ca (HCO3)2
(3) When heated with ammonium salt ammonia gas is obtained.
Ca(OH)2 + 2NH4Cl → CaCl2 + 2NH3 + 2H2O
(4) Reactions of calcium hydroxide with chlorine give different products under different conditions. These are given as below:
(A) Ca (OH)2 + Cl2 CaOCl2 + H2O
(B) 2Ca (OH)2 + 2Cl2 2CaCl2 + 2H2 O+ O2
(C) 2Ca (OH)2 + 2Cl2 → CaCl2 + + 2H2O
(cold and dil) (Calcium chlorate)
(D) 6Ca (OH)2 + 6Cl2 → 5CaCl2 + Ca(ClO3)2 + 6H2O
(hot and conc.) (Bleaching powder)