Sodium Carbonate

Washing soda

↪ Molecular formula: Na₂CO₃.10H₂O
↪ Chemical name: Sodium Carbonate

↪ It is the most important carbonate of metal.
↪ It occurs as anhydrous form, Na₂CO₃ which is called light soda ash since it is a fluffy solid with low packing density.
↪ Monohydrate form of sodium carbonate (Na₂CO₃.H₂O) is called heavy ash.
↪ Its heptahydrate form, (Na₂CO₃.7H₂O) also exists.
↪ Its decahydrate form, (Na₂CO₃.10H₂O), is white crystalline solid and is called washing soda.
↪ It occurs in nature as "trona" (Na₂CO₃.NaHCO₃.2H₂O) which gives sodium carbonate on heating.
            
Properties

⁕ Physical Properties

1. It is crystalline solid.
2. It is soluble in water.
3. It is efflorescent and it loses nine molecules of water when it is heated up to 100°C and above 100°C it loses all molecules of water and becomes anhydrous.   
   
4.  Anhydrous sodium carbonate melts at 852.1°C.
   

⁕ Chemical Properties

1. Action with water
   ↪ Sodium carbonate dissolves in water to give carbonic acid and caustic soda.
   
2. Action with acids
   ↪ It reacts with acids to give salt, water and carbon dioxide. 
   
3. Precipitation Reaction
   ↪ Sodium carbonate reacts with some metallic salt solution to give precipitate of their carbonate.
    
   
4. Action with Sulphur Dioxide
   ↪ Sodium carbonate reacts with Sulphur dioxide sodium sulphite and CO₂.
   
   ↪ But in presence of Sulphur it gives sodium thiosulphate  
   
5. Action with lime water
   ↪ On boiling with lime water, it produces caustic soda and calcium carbonate.
   
6. Action with CO₂
   ↪ When CO₂ gas is passed in the aqueous solution of Na2CO3, it forms insoluble sodium bicarbonate (NaHCO₃).
   
7. Action with silica (sand)
   ↪ When Na₂CO₃ is heated with silica, sodium silicate is formed. 
   

⁕ Uses of Sodium Carbonate

1. It is used in paper, paints and textile industries.
2. It is used in washing propose in laundry.
3. It is used in the manufacture of glass, borax, soap, hypo etc.
4. It is used as laboratory reagent.
5. It is used for softening of hard water.