CALCIUM OXIDE (CaO)
Preparation of CaO:
It is manufactured by heating lime stone below 1000ºC.
CaCO3 CaO + CO2
If the temperature exceeds 1000ºC then there is the possibility of forming silicates
Properties:
(1) It is white amorphous powder
(2) It is extremely stable, however it reacts with water in an exothermic way to form slaked lime. Its paste in water is called milk of lime. While its clear solution it is called lime water.
CaO + H2O → Ca(OH)2
(3) Being basic it reacts with acids or acidic oxides to form salt.
(A) CaO + 2HCl → CaCl2 + H 2O
(B) CaO + SiO2 CaSiO3
(C) 3CaO + P2O5
(4) In aqueous solution it reacts with CO2, SO2 and Cl2
(A) CaO + H2O → Ca (OH)2
(B) Ca (OH)2 + CO2 → CaCO3 + H2O
(C) Ca (OH)2 + Cl2 → CaOCl2 + H2O
(5) Calcium oxide when heated with carbon at 2270 K calcium carbide is formed. Which further
reacts with H2O to form acetylene and with nitrogen to form calcium cyanide.
CaO + 3C
CaC2 + 2H2O → Ca (OH)2 + C2H2
CaC2 + N2
(6) It reacts with ammonium chloride to form ammonia.
CaO + 2NH4Cl → CaCl2 + 2NH3 + H2O