Salts

Salts:

Salts are regarded as compounds made up of posi­tive and negative ions. The positive part comes from a base while negative part from an acid. Salts are ionic compounds. Salts may taste salty, sour, bitter, astringent or sweet or tasteless. Solutions of salts may be acidic, basic or neutral. Fused salts and aqueous solutions of salts conduct electricity and undergo electrolysis. The properties of salts in aqueous solutions are the properties of ions. The salts are generally crystalline solids.

The salts are classified into the following classes:

(i)      Simple salts:

The salt formed by the neutralization process, i.e., interaction between acid and base, is termed as
simple salt. These are of three types:

(a)     Normal salts:             The salts formed by the loss of all
possible protons (replaceable hydrogen atoms as H⁺) are called normal salts. Such a salt does not contain either a replaceable hydrogen or a hydroxyl group.

Examples are: NaCl, NaNO₃, K₂SO₄, Ca₃(PO₄)₂, Na₃BO₃, Na₂HPO₃ (one H atom is not replaceable as H₃PO₃ is a dibasic acid), NaH₂PO₂ (both H atoms are not replaceable as H₃PO₂ is a monobasic acid), etc.

(b)   Acid salts:       Salts formed by incomplete neutralization of poly-basic acids are called acid salts. Such salts still contain one or more replaceable hydrogen atoms. These salts when neutralised by bases form normal salts.

Examples are: NaHCO₃, NaHSO₄, NaH₂PO₄, Na₂HPO₄, etc.,

(c)   Basic salts:     Salts formed by incomplete neutralization of poly acidic bases are called basic salts. Such salts still contain one or more hydroxyl groups. These salts when neutralised by acids form normal salts.

Examples are: Zn(OH)Cl, Mg(OH)Cl, Fe(OH)₂Cl, Bi(OH)₂Cl, etc.

Double salts:

The addition compounds formed by the combination of two simple salts are termed double salts. Such
salts are stable in solid state only.

Examples are: Ferrous ammonium sulphate, FeS0₄-(NH₄)₂SO_4.6H₂O, Potash alum, K₂SO₄Al₂(SO₄)₃.24H₂O, and other alums.