Sodium hydroxide

02 Acid, bases and salt


  • 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:
Sodium hydroxide
  • 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.


  • 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.


  • 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).


  • 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).


  • 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’.

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