The principles of electrolysis are used in the manufacture of chemicals, like caustic soda (NaOH), chlorine gas, aluminium sulphate, potassium permanganate, hydrogen and oxygen on large scale.
The production of caustic soda when a solution of sodium chloride is electrolysed is obtained by following reaction:
The negative chloride (CI) moves towards the anode where they give up the negative charge and become Cl2.
ADVERTISEMENTS:
The positive sodium ions (Na+) move towards the cathode, giving up their positive charge and become sodium atoms (Na).
These sodium atoms react with water to liberate hydrogen and forming NaOH as per the following equation:
Usually, the brine is fed into the anode compartment to resist the flow of hydroxyl ions towards the anode. The voltage per cell required is about 3 – 4 volts and the current is of order of about 10,000 Amps.
ADVERTISEMENTS:
Brine is the one of the most important chemicals used for the manufacture of chlorine and sodium hydroxide is left in the vessel.
Production of Hydrogen and Oxygen by Electrolysis of Water:
The electrodes are of iron and the electrolyte consists of 20 percent solution of caustic soda. The gases obtained by this process are of high purity and cheap in cost due to low energy consumption.
The chemical reactions are in manufacturing of hydrogen and oxygen.
Therefore hydrogen and oxygen are liberated at the cathode and anode respectively and water vanished, the quantity of NaOH remaining constant. Therefore it is necessary to add water to the solution periodically.