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.

Shakeel Anwar Updated: Jan 31, 2017 15:49 IST

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.

Jagranjosh

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 –

Jagranjosh

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 → Na₂CO₃+ 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, Na₂B₄0_7.10 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 (NaCO_3.10 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.