SALTS

SALTS

A salt is formed by the combination of acid and base. 

The acidic and basic nature of salts depends on the acid and base combined in neutralization reaction.

 

Types of salts-

Types of salts

Combination of

pH

Examples

Acidic salt

strong acid and strong base

less than 7

Zinc sulphate(ZnSO4),

Copper sulpahte(CuSO4), etc

Basic salt

weak acid and strong base

more than 7

Sodium carbonate (Na2CO3), Sodium hydrogen carbonate(NaHCO3), etc

Neutral salt

strong acid and strong base

or

weak acid and weak base

equal to 7

Sodium chloride(NaCl), potassium chloride(KCl), etc

 

Some common salts-

Common Name

Chemical name

Chemical formula

Uses

Washing soda

Sodium carbonate decahydrate

  • It is used for manufacture of borax, and  caustic soda etc.
  • It is used in glass, soap and paper industries.
  • It is used for removing permanent hardness of water.

 

Baking soda

It is produced using sodium chloride as one of the raw materials.

 

 

Sodium hydrogen carbonate

 

  • It is used as an ingredient of baking powder(Baking powder is the mixture of baking soda and mild acid (tartaric acid))

 

  • The baking soda is commonly used in the kitchen for making tasty crispy pakoras, etc. 
  • It is added for faster cooking.
  • Carbon dioxide produced during the reaction can cause bread or cake to rise to make them soft and spongy.
  • Sodium hydrogen carbonate is also an ingredient in antacids. Being alkaline, it neutralizes excess acid in the stomach and provides relief. 
  • It is also used in soda-acid fire extinguishers.

 

Bleaching powder

Calcium oxychloride

 

  • Bleaching powder is used as an oxidizing agent in chemical industries.
  • It is used for bleaching cotton and linen in the textile industry, wood pulp in paper factories, and washed clothes in the laundry.
  • It is used for disinfecting drinking water.
  • Bleaching powder reacts with acids to produce chlorine gas.
  • CaOCl2 + H2SO4 → CaSO4 + Cl2 + H2O
  • The Cl2 produced by the action of dilute acid acts as the bleaching agent.

 

Plaster of Paris(P.O.P)

Calcium Sulphate Hemihydrate

CaSO4.1/2H2O

  • Used in hospital for setting fractured bones in the right position to ensure correct healing.
  • Making toys, decorative materials, cheap ornaments, and casts of statues.
  • Used as fire-proofing material.
  • Used in chemistry labs for setting air gaps in apparatus.
  • Making smooth surfaces, such as for  designs on ceilings of houses and other buildings 
  • It has a remarkable property of setting into hard mass on wetting with water.

 

Common salt/table salt

Sodium chloride

NaCl

  • It is used in food industry for preservation.
  • It is used for the production of sodium hydroxide, sodium carbonate, baking soda etc.
  • It is used for de-icing of roads.
  • Aqueous solution of sodium chloride is called brine solution.
  • When electricity is passed through brine solution, it decomposes to form sodium hydroxide, chlorine(at anode) and hydrogen gas(at cathode). This process is known as Chlor-alkali process.

 

Potash salt

Potassium aluminium sulphate

K2(SO4)•Al2(SO4)3•24H2O

  • It is a double salt.
  • It is also known as fitkari.
  • It is also known as potassium aluminium sulphate.
  • It is used in the manufacturing of drug, as a colour bonding in colouration, in the leather industry etc.
  • Alum is used as a waterpurifier.

 

Mohr salt

Ammonium iron(II) sulphate

FeSO4.(NH4)2SO4.6H2O

  • It is a double salt.
  • Mohr’s salt is easy to keep in laboratories in the form of crystals because it is resistant to oxidation.
  • Color of mohr’s salt crystals - Light green
  • The shape of mohr’s salt crystals – octahedral
  • Solubility - Readily soluble in water
  • The action of blue litmus paper - Blue litmus paper turns red

 

 

Water of crystallization –

Water of crystallization is the fixed number of water molecules present in one formula unit of a salt.

  • It is also known as water of hydration. 
  • The salts that contain water of crystallization are called hydrated salts.

For example –