Electrolysis of a concentrated aqueous solution of sodium chloride results in the formation of Sodium Hydroxide.
It is a whitish solid. It is available in flakes, pellets and granules.
It is soluble in a polar solvent such as water but it is insoluble in non-polar solvents such as ether.
Preparation of sodium hydroxide: The synthesis of sodium hydroxide takes place through the chlor-alkali process because NaOH (an alkali) and chlorine gas are present in final product.
Electricity is passed through a concentrated solution of sodium chloride called brine.
This Brine decomposes to form sodium hydroxide, chlorine and hydrogen:
During electrolysis, chlorine gas is been produced at the anode, which is the positive electrode and hydrogen gas is produced at the cathode, which is the negative electrode.
This forms sodium hydroxide solution near the cathode.
The products of electrolysis of sodium chloride solution, chlorine, hydrogen and sodium hydroxide, are then collected and stored separately.
USES OF SODIUM HYDROXIDE
It is used for making soaps and detergents.
It is used for making artificial textile fibres (such as rayon).
It is used in the manufacture of paper.
It is used in purifying bauxite ore from which aluminium metal is extracted.
It is used in de-greasing metals, oil refining, and making dyes and bleaches.6.
It is used to remove sulfurous impurities from poor quality crude oil. The process is called caustic washing.
USES OF CHLORINE
It sterilizes drinking water supply, and the water in swimming pools.
This is because chlorine is a disinfectant which kills germs like bacteria present in water and makes it safe.
It is used in the production of bleaching powder.
It is used in the production of hydrochloric acid.
It is used to make plastics such as polyvinyl chloride (PVC), pesticides, chlorofluorocarbons (CFCs), chloroform, carbon tetrachloride, paints and dye-stuffs.
It is used for making solvents for dry-cleaning (such as trichloroethane).
USES OF HYDROGEN
It is used in the hydrogenation of oils to obtain solid fats (called vegetable ghee or margarine).
It is used in the production of hydrochloric acid.
It is used to make ammonia for fertilizers.
It is used to make methanol (CH3OH).
Liquid hydrogen is used as a fuel for rockets.
The two products of the chlor-alkali process which are hydrogen and chlorine combine to produce another very important chemical called hydrochloric acid (HCl).
USES OF HYDROCHLORIC ACID
It is used for cleaning iron sheets before tin-plating or galvanisation.
It is used in the preparation of chlorides such as ammonium chloride (which is used in dry cells).
It is used in medicines and cosmetics.
It is used in textile, dyeing and tanning industries.
It is used in making plastics like polyvinyl chloride (PVC).
The two products of the chlor-alkali process, i.e. sodium hydroxide and chlorine, combine together to form another chemical called sodium hypochlorite (NaClO).
Sodium hypochlorite is a bleaching agent which is used in making ‘household bleaches’ and for ‘bleaching fabrics’.
