Saved Bookmarks
| 1. |
Starting with sodium chloride how would proceedto prepare (i) sodium metal (ii) sodium hydroxide (iii) sodium peroxide and (iv) sodium carbonate ? |
|
Answer» SOLUTION :(i) Sodium metal is manufacturedby electrolysis of a fused mixture of NaCl (40%) and `CaCl_(2)` (60%) in Down's cell at 873 K using iron cathode and graphite anode .Na is liberated at the cathode while `Cl_(2)` is evolved at the anode , At cathode : `Na^(+)` (melt) `+ e^(-) to Na (l)` At anode : `2 Cl^(-)` (melt) `to Cl_(2) (G) + 2 e^(-)` (ii) Sodium hydroxide is manufactured by electrolysis of an aqueous solution of NaCl (brine ) in CASTNER Kellner cell using mercury cathode and carbon anode . Sodium metal which is discharged at the cathode combines with mercury to form sodium amalgam . `Cl_(2)` gas is evolved at the anode . `{:("Cathode" : ,, Na^(+) + e^(-) to underset("Sodium")(Na) , ,, 2 Na + x HG to underset("Sodium amalgam")(Na_(2)Hg_(x))), ("Anode" : ,, 2Cl^(-) to Cl_(2) + 2 e^(-) ,,):} ` The sodium amalgam thus obtained is treated with water to form sodium hydroxide and hydrogen gas `Na_(2)Hg_(x) + 2H_(2)O to 2 NaOH + x Hg+ H_(2)` (iii) Sodium peroxide is obtained by HEATING sodium in excess of air . The intially formed sodium oxide reacts with more `O_(2)` to form `Na_(2)O_(2)`. `{:(4Na + O_(2) overset(Delta)(to) 2Na_(2)O), (2 Na_(2)O + O_(2) overset(Delta)(to) 2Na_(2)O_(2)):}` (iv) Sodium carbonate is obtained by Solvay ammonia process as discussed in Ans |
|