Quick lime, CaO: Preparation, Properties, Uses

Quick lime, CaO

Preparation

It is produced on a commercial scale by heating limestone in a lime kiln in the temperature range 1070-1270K.

CaCO3 ⇌  CaO + CO2

The reaction being reversible, 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.

It absorbs moisture and carbon dioxide on exposure to atmosphere.

CaO + H2O  → Ca(OH)2

CaO + CO2  → CaCO3

The addition of limited amount of water breaks the lump of lime. This process is called slaking of lime and the product is slaked lime.

CaO + H2O  → Ca(OH)2

Quick lime mixed with soda gives solid soda lime. It combines with acidic oxides such as SiO2 and P4O10 to form CaSiO3 and Ca3(PO4)2, respectively.

CaO + SiO2  → CaSiO3

6CaO + P4O10  → 2Ca3(PO4)2

Uses

Calcium oxide is used

i.              to manufacture cement, mortar and glass.

ii.               in the manufacture of sodium carbonate and slaked lime.

iii.               in the purification of sugar.

iv.               as a drying agent.