(N/A) Preparation: It is prepared on a commercial scale by heating limestone $(CaCO_{3})$ in a rotary kiln at $1070-1270 \ K$.
$CaCO_{3} \xrightarrow{\text{heat}} CaO + CO_{2}$
The carbon dioxide is removed as soon as it is produced to enable the reaction to proceed to completion.
Properties: Calcium oxide is a white amorphous solid. It has a melting point of $2870 \ K$. On exposure to the atmosphere,it absorbs moisture and carbon dioxide.
$CaO + H_{2}O \rightarrow Ca(OH)_{2}$
$CaO + CO_{2} \rightarrow CaCO_{3}$
The addition of a limited amount of water breaks the lump of lime. This process is called slaking of lime. Quick lime slaked with soda gives solid soda lime. Being a basic oxide,it combines with acidic oxides at high temperatures.
$CaO + SiO_{2} \rightarrow CaSiO_{3}$
$6CaO + P_{4}O_{10} \rightarrow 2Ca_{3}(PO_{4})_{2}$
Uses: $(i)$ It is an important primary material for manufacturing cement and is the cheapest form of alkali. $(ii)$ It is used in the manufacture of sodium carbonate from caustic soda. $(iii)$ It is employed in the purification of sugar and in the manufacture of dye stuffs.