- Books Name
- Ritan Sheth Chemistry Book
- Publication
- Ritan Sheth
- Course
- CBSE Class 11
- Subject
- Chemistry
SOME IMPORTANT COMPOUNDS OF SODIUM
1. Sodium Chloride, Common Salt or Table Salt [NaCI]
Sea water contains 2.7 to 2.9%by mass of the salt. Sodium chloride is obtained by evaporation of sea water but due to the presence of impurities like CaCl2 and MgCl2 it has deliquescens nature. It is purified by passing HCI gas through the impure saturated solution of
NaCl and due to common ion effect, pure NaCl gets precipitated. 28% NaCl solution is called brine.
2. Sodium Hydroxide or Caustic Soda [NaOH]
Methods of preparation
(i) A 10% solution of Na2CO3 is treated with milk of lime (Causticizing process).
Na2CO3 + Ca(OH)2 → CaCO3 ↓ + 2NaOH
(ii) Electrolytic process involves Nelson cell and Castner-Kellner cell.
A brine solution is electrolysed using a mercury cathode and a carbon anode. Sodium metal discharged at the cathode combines with Hg to form Na-amalgam. Chlorine gas is evolved at the anode.
The amalgam is treated with water to give sodium hydroxide and hydrogen gas.
2Na-Hg + 2H2O → 2NaOH + 2Hg + H2
Physical properties
Sodium hydroxide is a white translucent solid. It is readily soluble in water. Crystals of NaOH are deliquescent.
Chemical properties
1. It is a hygroscopic, deliquescent white solid, absorbs CO2 and moisture from the atmosphere
3. Sodium Carbonate or Washing Soda (Na2CO3 . 10H2O)
Solvay process
CO2 gas is passed through a brine solution saturated with NH3
Sodium bicarbonate is filtered and dried. It is ignited to give sodium carbonate.