Home | | Chemistry 11th std | Quick lime, CaO: Preparation, Properties, Uses

Chapter: 11th Chemistry : Alkali and Alkaline Earth Metals

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Quick lime, CaO: Preparation, Properties, Uses

Calcium oxide is a white amorphous solid.

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 + H2 → 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 + H2 → 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.


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