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Starting with sodium chloride how would you proceed to prepare (i) sodium metal (ii) sodium hydroxide (iii) sodium peroxide (iv) sodium carbonate? |
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Answer» (i) sodium metal:Sodium chloride can be converted into sodium by Downs process. It can be achieved by electrolysis of fused CaCl2 (60 %) and NaCl (40%) at 1123 K in a special apparatus (Downs cell). A graphite block is the anode while steel is made the cathode. Metallic Ca and Na are formed at the cathode. Molten Na is supported by dipping in kerosene. Nacl →Electrolysis Na+ + Cl– (Molten) At Cathode: Na+ +e– → Na At Anode: Cl– - e– → Cl (ii)Sodium Hydroxide: By electrolyzing a solution of sodium chloride, we can get Sodium hydroxide. This process is commonly known as Castner- Kellner process. The process is carried out using a mercury cathode and a carbon anode. Sodium metal, deposited at cathode forms an Amalgam by combining with Mercury. Cathode: Na+ +e– →Hg Na-Amalgam Anode; 2 Cl– → Cl2 + 2e– Cl + Cl → Cl2 (iii) Sodium peroxide: After Na metal is gotten from Downs process, it is heated on Aluminium trays in presence of air(without CO2) to form Sodium peroxide. 2Na + O2(air) → Na2O2 (iv) Sodium carbonate: Sodium hydrogen carbonate is obtained as a precipitate by reacting sodium chloride with ammonium hydrogen carbonate. The resultant crystals can be heated to obtain Sodium Carbonate. 2NH2 + H2O → (NH4)2CO3 (NH4)2CO3 + H2O + CO2 → 2NH4HCO3 2NH4HCO3 + NaCl → NH4Cl + NaHCO3 The resultant crystals can be heated to obtain Sodium Carbonate. 2NaHCO3 → Na2CO3+ CO2 + H2O |
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