About  salts

  1. Strong acid  +  strong base       neutral salt :  pH = 7
  2. Salt of strong   +  weak base      Acidic salt :    pH <7
  3. Salt of strong base + weak acid  Basic salt  :  pH  >7

Chemical from common salt

1;  sodium hydroxide  ( NaOH)

  When electricity is passed through an aqueous solution of NaCl (called brine) it decomposes to form NaOH.

This process is called chlor- alkali process.

2NaCl  +   2H2O              2NaOH + Cl2    + H2

 At cathode  :     H2    gas

 At anode :    Cl2 gas

Near cathode :   NaOH solution is formed

Uses

  1. Cl2 :   Water treatment , PVC , pesticides.
  2. H2 :      Fuels,  margarine.
  3. Hcl :       Medicines, cleaning steels.
  4.  NaOH :   De- greasing metals, soaps and paper making.

(2) Bleaching powder  ( CaOCl2)

   Bleaching powder is produced by the action of chlorine on dry slaked lime   ( Ca(OH)2).

 Cl2  +  Ca(OH)2        CaOCl2  +   H2O

 USES :   * Bleaching cotton and linen in textile industry

  • Bleaching washed clothes in laundry .
  • Oxidising in chemical industries.
  •  Make drinking water free from germs

(3)   Baking Soda ( NaHCO3)

 The chemical name of the compound is sodium hydrogen carbonate.

NaCl+H2O+CO2+NH3      NH4Cl  +  NaHCO3

                                     (Ammonium Chloride) (Sodium hydrogen carbonate)

  • IT is a mild non- corrosive base.
  • When it is heated during cooking.

2 NaHCO3      Na2CO3  +   H2O  +  CO2

USES:-

  1. For making baking powder, which is a mixture of baking soda ( sodium hydrogen carbonate ) and tartaric acid. Following reaction takes place.

 NaHCO3   +  H+         CO2  H2O + Sodium salt of acid

  1. Sodium hydrogen carbonate is an ingredient in antacids.
  2. Used in soda-acid , fire extinguisher

 (4)  Washing Soda  :-   ( Na2 CO3IOH2O)

  Recrystallisation of sodium carbonate gives washing sod. It is a basic salt.

  Na2CO3 + IOH2O     →    Na2CO3. IOH2O

   USES;   

  1. In glass , soap and paper industries.
  2. Manufacture of borax
  3. Cleaning agent for domestic purpose.
  4. For removing permanent hardness of water.

 (5)  Plaster of paris CaSO4 .2H2 O. 

On heating gypsum ( CaSo4.2H2O) at 373k, ut loses water molecules and becomes plaster of paris (POP) .

It is a white powder and on mixing with waater it changes to gypsum.

 Removing water of crystallization.

 WATER OF CRYSTALLISATION ;

It is a fixed number of water molecules present in one formula unit of a salt.

For Example; 

  • CuSO4.5H2O   has 5 water molecules.
  • Na2CO3.10H2  has 10 water molecules.
  •  CaSO4.2H2O  has 2 water molecules.