In the Down's cell KCl is added in NaCl to

Extraction of "Na" is done by down's processElectrolyte : Fused NaCl→ NaCl melting point is 1084K, it is difficult to attain and maintain this high temperature→ Its boiling point is 1156K and hence at the temperature of electrolysis, the metal liberated will vapourise.To over come these difficulties, we need to add CaCl2 & KF (or) KCl.The addition of CaCl2 & KF (OR) KCl lower the melting point of NaCl to 850-875KTherefore the Na liberated will not vapourise during electrolysis. NaCl dissociation is Na+ + Cl-At anode : Cl- → 1/2Cl2↑ + e-At cathode : Na+ + e- → Na