Periodic Table of Elements

Salts

Definition: The compounds containing positive annegative ions are known as salts. Salts are obtained by mixing an acid with a base.

Types of salts

Normal salts:

A salt that does not contain any replaceable hydrogen ions is a normal salt. It is obtained by replacing all the hydrogen (H+) ions of an acid by metal ions or ammonium ions. Normal salts are neutral.

Example:

Ca(OH)2 + 2HCl CaCl2 + H2O
In the above equation H+ in HCl is replaced by Na+.
H2SO4 + CuO CuSO4 + H2O

Acidic salts:

A salt that contains replaceable hydrogen ions is an acidic salt. It is obtained by partially replacing the hydrogen (H+) ions of an acid by metal ions or ammonium ions. Acidic salts are produced when each molecule of acid has more than 1 H+ ion. Example: H2SO4 Acidic salts are produced when there is an insufficient supply of metal ions or ammonium ions to replace all the H+ ions. These types of salts turn blue litmus to red.

Example:

H2SO4 + 2KOH K2SO4 + 2H2O

Basic salts:

A salt that contains replaceable hydroxyl groups is a basic salt. It is obtained when there is an insufficient supply of acid H+ ions to completely neutralize the base.

Example:

Zn(OH)2 + 2HNO3 Zn(NO3)2 + 2H2O

Double salts:

Double salts are salts containing more than one cation or anion. Double salt is a salt that ionizes to produce three different types of ions in solution, two of these are usually positively charged and the other negatively charged. Double salts are formed by the combination of two simple salts.

Examples are ammonium iron(II) tetraoxosulphate(VI) hexahydrate, (NH4)2Fe(SO4)2.6H2O
potash alum or aluminium potassium tetraoxosulphate(VI) dodecahydrate, KAl(SO4)2.12H2O
chrome alum or chromium(III) potassium tetraoxosulphate(VI) dodecahydrate, KCr(SO4)2.12H2O

Complex salts:

A salt that contains complex ions, i.e. ions consisting of a charged group of atoms is a complex salt.

Example:

K2[Fe(CN)6] 4K+ + [Fe(CN)6]4-
Potassium ferrocyanide simple ion + complex ion

Mixed salts:

Salts that contain more than one type of cation or anion are called as mixed salts.

Example:

Bleaching powder - CaoCl2
Sodium potassium sulphate - NaKSO4