(N/A) Preparation: Calcium hydroxide is prepared by adding water to quick lime,$CaO$.
$CaO + H_2O \rightarrow Ca(OH)_2$
Properties: It is a white amorphous powder. It is sparingly soluble in water. The aqueous solution is known as lime water,and a suspension of slaked lime in water is known as milk of lime. When carbon dioxide is passed through lime water,it turns milky due to the formation of calcium carbonate.
$Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$
On passing an excess of carbon dioxide,the precipitate dissolves to form calcium hydrogen carbonate.
$CaCO_3 + CO_2 + H_2O \rightarrow Ca(HCO_3)_2$
Milk of lime reacts with chlorine to form hypochlorite,a constituent of bleaching powder:
$2Ca(OH)_2 + 2Cl_2 \rightarrow CaCl_2 + Ca(OCl)_2 + 2H_2O$
Uses: $(i)$ It is used in the preparation of mortar,a building material. $(ii)$ It is used in white washing due to its disinfectant nature. $(iii)$ It is used in glass making,in the tanning industry,for the preparation of bleaching powder,and for the purification of sugar.