CBSE Class 10 Answered

Sodium is extracted from molten sodium chloride in a Down's cell electrolytically. 

Sodium chloride has a high melting point, ~800^oC, so calcium chloride or sodium carbonate is added to reduce the melting point to around 600^oC

The products of the electrolysis of molten (fused) sodium chloride are sodium metal and chlorine gas.

Sodium is produced at the cathode: Na⁺  +  e⁻  →  Na

And chlorine is given off at the anode: 2Cl⁻  −  2e⁻  →  Cl₂

The two elements are kept apart by a steel gauze in the cell.

In the Down's Cell a circular iron cathode surrounds the carbon anode and the products of the electrolysis are separated by steel mesh or gauze to prevent them coming into contact and reforming sodium chloride.

The amount of sodium produced can be calculated using Faraday's Laws of Electrolysis.