Question

EXTRACTION OF SODIUM BY DOWN 'S PROCESS. EXPLAIN WITH CONSTRUCTION AND WORKING.

Answer 1

"Down's Process" is used for the extraction of Sodium (Na) on industrial scale.

Principle : 

This Process is based on the electrolysis of fused NaCl.

Construction :

⇒Down's cell consists of a rectangular container of steel.
⇒Inside of the tank is lined with firebricks.
⇒Anode is a graphite rod which projects centrally up through the base of the cell.
⇒Cathode is a ring of iron, which surrounds the anode.
⇒The anode and cathode are separated from each other by a cylindrical steel gauze diaphragm so that Na and Cl₂ are kept apart.
⇒A bell like hood is submerged over the anode.

Process :

when a passage electric current is passed through the molten mixture of NaCl and CaCl₂, NaCl decomposes in to  Na⁺ and Cl⁻ ion.

Na⁺ ions migrate towards cathode while Cl⁻ ions towards the anode. The molten sodium  gets collected into the cathode compartment where it rises to the top and is tapped off by a pipe. Chlorine is collected at the anode.

Working :

As NaCl decomposes,

NaCl → Na⁺ + Cl⁻

At anode , 
Na⁺ + 1e⁻ → Na

At cathode, 
Cl⁻ - e⁻ → Cl + e⁻
Cl + Cl → Cl₂

Overall Reaction :

Na⁺ + Cl⁻ → Na + Cl
2Na⁺ + 2Cl⁻ → 2Na + Cl₂

I hope it helps you ^_^