Class 10 Science

Chemicals From Common Salt

Common salt or sodium chloride is the starting material for making many useful chemicals. On this page, you will learn about chlor-alkali process. You will also learn about caustic soda and bleaching powder.

These notes are based on the chapter Acids Bases and Salts from NCERT book based on CBSE syllabus.

  • Sodium hydroxide or caustic soda
  • Bleaching powder

Common Salt (Sodium Chloride)

Sodium chloride (NaCl) is also known as common or table salt.

It is formed after the reaction between sodium hydroxide and hydrochloric acid. It is a neutral salt. The pH value of sodium chloride is about 7.

Sodium chloride is used to enhance the taste of food. Sodium chloride is used in manufacturing of many chemicals. In this section, you will read about sodium hydroxide, bleaching powder and sodium bicarbonate.

Chlor-Alkali Process

The electrolytic decomposition of brine is called chlor-alkali process. In the process of electrolytic decomposition of brine (aqueous solution of sodium chloride), brine decomposes to form sodium hydroxide. In this process, chlorine is obtained at anode and hydrogen gas is obtained at cathode as byproducts. This whole process is known as Chlor-Alkali process. As, chlorine and sodium hydroxide (alkali) are key products of this process so it is called chlor-alkali process.

2NaCl + 2H2O ⇨ 2NaOH + Cl2 + H2

Use of products after electrolysis of brine:

  • Hydrogen gas is used as fuel, margarine, in making of ammonia for fertilizer, etc.
  • Chlorine gas is used in water treatment, manufacturing of PVC, disinfectants, CFC, pesticides. It is also used in manufacturing of bleaching powder and hydrochloric acid.
  • Sodium hydroxide is used for de-greasing of metals, manufacturing of paper, soap, detergents, artificial fibres, bleach, etc.

Sodium Hydroxide (NaOH)

Sodium hydroxide is a strong base. It is also known as caustic soda or Lye. It is obtained by chlor-alkali process.

Bleaching Powder (CaOCl2)

Bleaching powder is also known as chloride of lime. It is a solid and yellowish white in colour. Bleaching powder can be easily identified by the strong smell of chlorine.


When calcium hydroxide (slaked lime) reacts with chlorine, it gives calcium oxychloride (bleaching powder) and water is formed.

Ca(OH)2 + Cl2 ⇨ CaOCl2 + H2O

Aqueous solution of bleaching powder is basic in nature. The term bleach means removal of colour. Bleaching powder is often used as bleaching agent. It works because of oxidation. Chlorine in the bleaching powder is responsible for bleaching effect.

Use of bleaching powder

  • Bleaching powder is used as disinfectant to clean water, moss remover, weed killers, etc.
  • Bleaching powder is used for bleaching of cotton in textile industry, bleaching of wood pulp in paper industry.
  • Bleaching powder is used as oxidizing agent in many industries, such as textiles industry, paper industry, etc.

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