Acids, Bases and Salts — Part 3: Chemicals from common salt: visual lesson, CBSE Class 10 Science

Lesson

Chemicals from common salt

Part 3 — how one cheap raw material, sodium chloride, becomes sodium hydroxide, bleaching powder, baking soda and washing soda, plus plaster of Paris from gypsum.

In this lesson you will

Describe how common salt is obtained from sea water and rock salt
Describe the chlor-alkali process and the uses of its products
Write equations for making bleaching powder, baking soda and washing soda
State the uses of bleaching powder, baking soda, washing soda and plaster of Paris
Explain how plaster of Paris is made from gypsum and how it sets with water

Diagram

Where common salt comes from

Gujarat and Tamil Nadu produce most of India’s sea salt this way.

Sea water is evaporated in shallow salt pans. Rock salt is mined from beds left where ancient seas dried up. Crude salt contains impurities and is purified before use.

Diagram

Electrolysis of brine

Chlorine is poisonous: industrial cells keep the two gases apart.

Passing electricity through brine, a concentrated solution of sodium chloride, gives chlorine at the anode, hydrogen at the cathode and sodium hydroxide solution near the cathode.

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