Reactions:
2Na/Hg+2H2​O→2NaOH+H2​+Hg

It is generally prepared by electrolysis of sodium chloride in Castner-kellner cell. A brine solution is electrolyzed using mercury cathode and carbon anode. Sodium metal, discharged at the cathode, combine with mercury to form sodium amalgam. Cl gas is evolved at the cathode. The amalgam is treated with water to give sodium hydroxide and hydrogen gas.
Reactions:
2Na/Hg+2H2​O→2NaOH+H2​+Hg

Chemical Reaction for the Preparation of Sodium Hydroxide

The preparation of sodium hydroxide (NaOH) involves a chemical reaction known as the chloralkali process. This process consists of several steps, including the electrolysis of a sodium chloride (NaCl) solution.

1. Electrolysis of Sodium Chloride Solution:
The first step in the preparation of sodium hydroxide is the electrolysis of a sodium chloride solution. This process occurs in an electrolytic cell, which consists of two electrodes, namely a cathode and an anode, immersed in the electrolyte solution.

2. Cathode Reaction:
At the cathode (negative electrode), water molecules (H2O) are reduced to produce hydrogen gas (H2) and hydroxide ions (OH-). The cathode reaction can be represented as follows:

2H2O + 2e- -> H2 + 2OH-

3. Anode Reaction:
At the anode (positive electrode), chloride ions (Cl-) are oxidized to produce chlorine gas (Cl2). The anode reaction can be represented as follows:

2Cl- -> Cl2 + 2e-

4. Overall Reaction:
The overall reaction that occurs during the electrolysis of sodium chloride solution can be represented as follows:

2NaCl + 2H2O -> Cl2 + H2 + 2NaOH

Explanation:
During the electrolysis process, the positively charged sodium ions (Na+) move towards the cathode, while the negatively charged chloride ions (Cl-) move towards the anode. At the cathode, water molecules are reduced, producing hydroxide ions and hydrogen gas. At the anode, chloride ions are oxidized, producing chlorine gas.

The hydroxide ions formed at the cathode combine with the remaining sodium ions in the solution to form sodium hydroxide (NaOH). This reaction is responsible for the production of sodium hydroxide.

Finally, the chlorine gas and hydrogen gas produced during electrolysis are separated and collected for further use or disposal.

Conclusion:
The preparation of sodium hydroxide involves the electrolysis of a sodium chloride solution. The cathode reaction produces hydroxide ions and hydrogen gas, while the anode reaction produces chlorine gas. The hydroxide ions combine with sodium ions to form sodium hydroxide, which is collected as the final product. This process is widely used in industries for the large-scale production of sodium hydroxide.