s-Block Elements : CALCIUM OXIDE (CaO)

CALCIUM OXIDE  (CaO)

Preparation of CaO:

It is manufactured by heating lime stone below 1000ºC.

                                      CaCO3 \underrightarrow { \quad 100{ 0 }^{ 0 }C\quad } 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 \underrightarrow { \quad \Delta \quad } CaSiO3

                   (C)    3CaO + P2O5 \underrightarrow { \quad \Delta \quad } Ca3 (PO4)2

(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  \underrightarrow { \quad 2270\quad K\quad } CaC2 + CO

                             CaC2 + 2H2O → Ca (OH)2 + C2H2

                             CaC2 + N2 \underrightarrow { \quad 1330\quad K\quad } CaCN2 + C

(6)     It reacts with ammonium chloride to form ammonia.

                             CaO + 2NH4Cl → CaCl2 + 2NH3 + H2O