Sodium Hydroxide ( Caustic Soda ) NaOH

Sodium Hydroxide also known as Caustic Soda (NaOH) Preparation : i. Electrolysis of Brine : Sodium hydroxide is generally prepared commercially by the electrolysis of sodium chloride in Castner-Kellner cell. A brine solution is electrolysed using a mercury cathode and a carbon anode. Sodium metal discharged at the cathode combines with mercury to form sodium amalgam. Chlorine gas is evolved at the anode. The amalgam is treated with water to give sodium hydroxide and hydrogen gas. Cathode : Na+ + e- --Hg--> Na-amalgam Anode : Cl- --> 1/2 Cl2 + e- 2Na-amalgam + 2H2O --> 2NaOH + 2Hg + H2 2. Caustication of Na2CO3 (Gossage method) Na2CO3 + Ca(OH)2 --> 2NaOH + (suspension) CaCO3 Ksp (CaCO3) < Ksp (Ca(OH)2), the reaction shifts towards right. Properties : 1. Sodium hydroxide is a white, translucent solid. It melts at 591 K. It is readily soluble in water to give a strong alkaline solution. Crystals of sodium hydroxide are deliquescent. The sodium hydroxide solution at the surface reacts with the CO2 in the atmosphere to form Na2CO3. 2. It is white crystalline, deliquescent, highly corrosive solid. 3. It is stable towards heat. 4. Its aqueous solution alkaline in nature and soapy in touch. 5. Acidic and amphoteric oxides gets dissolved easily 6. Aluminium and Zn metals hues H2 from NaOH. 7. Several non metals such as P, S, Cl. Yields a hydride instead of hydrogen Uses : It is used in i. The petroleum refining. ii. The manufacture of soap, paper, Artificial silk and a number of chemicals. iii. In the purification of bauxite iv. In the textile industries for mercesing cotton fabrics. v. For the preparation of pure fats and oils vi. As a laboratory reagent.