Sodium Hydroxide - Preparation, Properties and Uses
Properties of sodium hydroxide
1. It is stable towards heat. 2. It is highly soluble in water and a considerable amount of heat is evolved due to the formation of a number of hydrates, e.g., NaOH.H2O, NaOH.2H2O. It is also soluble in alcohol. 3. Aqueous solution of sodium hydroxide is strongly alkaline due to its complete dissociation into Na+ and OH−
Uses of sodium hydroxide
1. In the refining of petroleum and vegetable oils. 2. In the purification of bauxite for the extraction of aluminium. 3. As a cleansing agent and in washing powder for machines, metal sheets etc.
Method of prepration of sodium hydroxide
It is generally prepared by electrolysis of sodium chloride in Castner-kellner cell. A brine solution is electrolyzed using mercury cathode and carbon anode. Sodium metal, discharged at the cathode, combine with mercury to form sodium amalgam. Cl gas is evolved at the cathode. The amalgam is treated with water to give sodium hydroxide and hydrogen gas. Reactions: 2Na/Hg+2H2O→2NaOH+H2+Hg