Acids, Bases and Salts

3. Salts

Salts

The ionic compounds formed when acid and base react with each other are called Salts. That is, a salt is a compound consisting of positive metallic ion and a negative ion.

e.g. NaCl; Sodium chloride

Acid + Base → Salt + Water 

1. Salts are neutral in nature. 
2. The salts are formed because of neutralization reaction as both acid and base neutralize each other’s effect. 

Examples:

• Sodium chloride (common salt) CaCl_2,
• Barium sulphate (BaSO₄)
• Sodium nitrate (NaNO₃) 

Sodium chloride or common salt is a product of the neutralisation reaction between the hydrochloric acid (acid) and sodium hydroxide (base). 

 

Neutralization:  

The reaction between a base and an acid to produce salt and water is called Neutralisation. 

For example:

• When sodium hydroxide (NaOH), a base reacts with sulphuric acid (H₂SO₄), it forms salt, i.e., sodium sulphate and water. 

In all neutralization reactions, the product is always water due to the combination of hydrogen ions present in the acid and hydroxyl ions present in the base.  

The formation of water in an acid-base occurs as follows: 

Types Of Salts

Five main types of salts exist which are:

1. Normal salt: Normal salt is formed when all the replaceable hydrogen ions in an acid have been completely replaced by metallic ions of a base. E.g. NaCl, CaCl₂, MgSO₄, Na₂SO₄.

A normal salt contains no replaceable hydrogen, H⁺ or hydroxyl, OH^-, ion. Aqueous solution of normal salt is neutral to litmus and it has a pH of 7.

2. Acid salt: An acid salt is formed when the replaceable hydrogen ions in the acid are partially replaced by a metal. An acid salt contains replaceable hydrogen ion E.g NaHCO₃; sodium hydrogen trioxocarbonate(iv). NaHSO₄; Sodium hydrogen tetraoxosulphate (vi) Ca(HCO₃)₂;Calcium hydrogen trioxocarbonate(iv).

A solution of an acidic salt turns blue litmus paper red, and it can react with excess alkali to form

a normal salt and water. Eg.

3. Basic salt: A basic salt is formed when a base reacts with a limited quantity of an acid. That is, the oxonium ion, H₃O⁺, is insufficient for the complete neutralization of the base. A basic salt therefore contains replaceable hydroxyl ions, OH^-.

 

4. Double salt: Double salt is a salt which ionizes to yield three different types of ions in solution.

Two of than are positively charged (metallic ions) while the other is negatively charged. Eg

(NH₄)SO₄FeSO₄.6H₂O Ammonium iron(ii) tetraoxosulphate(vi) hexahydrate

KAl(SO₄)₂ .12H₂O Ammonium potassium tetroxosulphate (vi) dodecahydrate

5. Complex salt: This is a salt that contains complex ions. A complex ion is the ion consisting of a

charged group of atoms. E.g.