Preparation of Fluorine by Electrolysis
Fluorine gas is prepared by the electrolysis of a solution of potassium fluoride (KF) in hydrogen fluoride (HF) at a temperature of around 70 degrees Celsius. This process is carried out in a specially designed electrolytic cell known as the Castner-Kellner cell.

Electrolysis Process
- In the Castner-Kellner cell, two electrodes are used - one made of carbon and the other of iron.
- When an electric current is passed through the electrolyte solution of KF in HF, fluoride ions (F-) are discharged at the anode (carbon electrode).
- These fluoride ions combine to form fluorine gas (F2), which is collected at the anode.
- At the cathode (iron electrode), hydrogen gas is produced due to the reduction of hydrogen ions (H+).

Chemical Reaction
The overall chemical reaction that takes place during the electrolysis of KF in HF is:
2KF (aq) + 2H2O (l) -> 2KOH (aq) + H2 (g) + F2 (g)
This reaction shows the formation of potassium hydroxide (KOH), hydrogen gas (H2), and fluorine gas (F2) as products.

Significance
Fluorine is a highly reactive element and is not found in its pure form in nature. Therefore, the electrolysis process is essential for obtaining fluorine gas for various industrial applications, such as the production of fluorocarbons, fluorides, and other fluorine-containing compounds.