Chemicals from salts

1. SHIKHA CHOUDHARY CHEMISTARY X A

2. CHEMICALS FROM SALTS What are salts? - When a metal combines with an acid, it forms a compound called a salt. Reaction: Acid+ Metal Salt+ Hydrogen gas For ex. NaOH(aq)+HCl(aq) NaCl(aq)+ H 2 O(l)

3. COMMON SALT Salt formed by the combination of hydrochloride acid & sodium hydroxide solution is called sodium chloride. This is the salt we use in food. It is a neutral salt or common salt. Seawater contains many salts dissolved in it. Sodium chloride is separated from these salts.

4. Deposits of solid salt are also found in several parts of the world. These large crystals are often brown due to the impurities. This is called rock salt. Beds of rock salt were formed when seas of bygone ages dried up. Rock salt is mined like coal.

5. Raw material for Chemicals The common salt is an important raw material for various materials of daily use. Some of those are:

6. Sodium Hydroxide When electricity is passed through a saturated aqueous solution of sodium chloride (brine), it decomposes to form sodium hydroxide. This process is called chlor- alkali process because of the products formed – chlor for chlorine & alkali for sodium hydroxide. 2NaCl+2H 2 O 2NaOH+Cl 2 +H 2

7. Bleaching Powder The chlorine produced during the electrolysis of aqueous sodium chloride is used for the manufacture of bleaching powder. Bleaching powder is produced by the action of chlorine on dry slaked lime. Ca(OH) 2 + Cl 2 CaOCl 2 + H 2 O

8. Bleaching powder is used – For bleaching cotton & linen in the textile industry, for bleaching wood pulp in paper factories & for bleaching washed clothes in laundry. As an oxidising agent in many chemical industries. For disinfecting drinking water to make it free of germs.

9. Baking Soda The soda commonly used in the kitchen for making food crispy is baking soda. Sometimes it is added for faster cooking. The chemical name of the compound is sodium hydrogencarbonate. It is produced using sodium chloride as one of the raw materials. NaCl+H 2 O+CO 2 +NH 3 NH 4 Cl+NaHCO 3

10. Uses of sodium hydrogencarbonate For making baking powder, which is a mixture of baking soda &a mild edible acid such as tartaric acid. Sodium hydrogencarbonate is also an ingredient in antacids. Being alkaline, it neutralises excess acid in the stomach & provides relief. It is also used in soda- acid fire extinguishers.

11. Washing Soda Another chemical that can be obtained from sodium chloride is washing soda. Sodium carbonate can be obtained by heating baking soda; recrystallisation of sodium carbonate gives washing soda. It is also a basic salt. Na 2 CO 3 + 10H 2 O Na 2 CO 3 .10H 2 O

12. Uses of washing soda Sodium carbonate is used in glass, soap & paper industries. It is used in the manufacture of sodium compounds such as borax. Sodium carbonate can be used as a cleaning agent for domestic purposes. It is used for removing permanent hardness of water.

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