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Salt: Concept, properties and uses

Salt is an ionic compound that results from the neutralization reaction of an acid and a base.It is composed of related numbers of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge). They may be simple salts such as NaCl, KCl, and Na2SO4; acid salts like NaHCO3 and NaH2PO4; or double salts like KAl (SO4)2.
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Salt is an ionic compound that results from the neutralization reaction of an acid and a base.It is composed of related numbers of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge). They may be simple salts such as NaCl, KCl, and Na2SO4; acid salts like NaHCO3 and NaH2PO4; or double salts like KAl (SO4)2.

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In other words, a salt is a compound formed by partial or complete replacement of the replaceable hydrogen atoms from an acid molecule by means of metal or a radical which acts like a metal. For example –

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Types of Salts

Normal Salt: A normal salt is a salt formed by the complete replacement of replaceable hydrogen atoms from an acid molecule by means of a metal or a group of elements acting like a metal.  Examples: The compounds like KCl, NaCl, FeS04, Na2S04, FeCl2 etc are normal salts. Obviously a normal salt doesn't contain replaceable H-atom in its molecule.

Acid Salt: An acid salt is that which contains one or more replaceable hydrogen atoms in its molecule and is formed by partial replacement of H- atoms present in an acid molecule by means of metal or positive radical.  Examples: The compounds like NaHS04, NaHC03, KHC03, NaH2PO etc are acid salts.

Basic Salt

Basic Salt: A salt which contains 02- or OH- group in its molecule is called basic salt.  Examples: The compounds like Mg (OH) Cl, [Mg (OH)2 . MgC03], [Cu (OH) 2.CuCO3) etc are basic salts.

NH4OH + HCl → NH4Cl + H2O

Acidic Salt: A normal salt which is formed by the neutralisation of a strong acid and weak base is called acidic salt because its aqueous solution turns blue litmus red. Examples: The compounds like FeCI3, ZnCl2, HgCl2, Fe2 (S04)3, HgS04 etc are acidic salts.

2NaOH + H2CO3  Na2CO+ 2H2O

Alkaline Salt: Normal salts which are formed by the neutralisation of weak acids and strong bases are called alkaline salts because their aqueous solutions turn red litmus blue. Examples: The compounds like Na2C03, CH3COONa, Na2C204, Na2B407.10 H20 etc are alkaline salts.

NaOH + HCl  NaCl + H2O

Neutral Salt: They are formed by the neutralisation of strong acids and strong bases, are called neutral salts because their aqueous solutions are neutral to litmus.  Examples: The compounds like NaCl, KCl, K2S04, NaN03, KCl03, KClO4 etc are neutral salts.

Double Salt: A double salt is a mixture of two salts which on dissolution in water gives two types of metal ions.  Examples: The compounds like Potash Alum [K2S04. Al2 (S04)3. 24 H20], Mohr's salt [FeS04. (NH4)2S04. 6H20], Ferric Alum [K2S04. Fe2 (SO4)3.24 H20] etc are double salts.

Complex Salt: A complex salt is a salt which contains a complex ion or complex neutral molecule in which there is a central metal ion surrounded by a number of neutral molecules or negative ions.  Examples: The compounds like potassium ferrocyanide (K4[Fe(CN)6]), potassium argento cyanide (K [Ag(CN)2]) tetra amino cupric sulphate  ([Cu(NH3)4]SO4) etc are complex salts.

Uses of Salts

The uses of the salts are given below in tabular form:

Salts

Uses

Common Salt (NaCl) Sodium Chloride

  • Common salt is used in cooking gas.
  • It is used as a preservative in pickles and in curing meat and fish.
  • It is used in the manufacture of soap.
  • It is used to melt the ice in winter in cold countries.
  • Used in making large chemicals like washing soda, baking soda etc.

Sodium Hydroxide (NaOH)

  • Used for making soap and detergent.
  • used for making artificial textile fiber (rayon)
  • Used in the manufacture of paper.
  • Used in purifying bauxite ore.
  • Used in de-greasing metals, oil refining and making dyes and bleaches.

Washing Soda (NaCO3.10 H2O) Sodium Carbonate

  • Used as a 'cleansing agent' for domestic purposes like washing Clothes.
  • Used to remove permanent hardness of water.
  • Used in the manufacture of glass, soap and paper.
  • Used in the manufacture of sodium compounds such as borax.

Baking Soda (NaHCO3) Sodium Bicarbonate

  • Used as an antacid.
  • Used in making baking powder which is used in making cakes, bread etc.
  • Used in fire extinguishers.

Bleaching Powder (CaOCl2) Calcium hydro chlorite

  • Used in textile industry for bleaching cotton and linen and in paper.
  • Industry for bleaching wood pulp.
  • Used for disinfecting drinking water.
  • used in the manufacture of chloroform (CHCl3)
  • Used for making wool unshrinkable.
  • Used as oxidizing agent in many chemical industries.

Plaster  of Paris

CaS04 1/2 H2O)

Calcium sulphate

hemi hydrate

  • Used in hospital for setting fractured bone.
  • Used for making toys, decoration material cheap ornament, chalk etc.
  • used for fire-proofing material
  • Used for making surface smooth.

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