Acids, Bases and Salts - ICSE CLASS 10 CHEMISTRY NOTES

Acid - Definition - Classification of acids - ICSE CLASS 10

Acid: An acid is a compound which produces Hydronium ions (H₃O⁺) as the only positively charged ions in its aqueous solution.

Example : Hydrochloric acid, Sulphuric acid, Acetic acid etc.

Hydronium ions are responsible for the acid nature of a solution.

When HCl is dissolved in water it ionizes to form H⁺  and Cl^-. The Hydrogen ion (H⁺ or proton) combines with water molecule and forms Hydronium ion. Thus the resultant solution contains Hydronium ions and Chloride ions. The positively charged ions in this solution are Hydronium ions hence aqueous HCl (Hydrochoric acid) is considered an acid.

 

Classification of acids:

1.      Based on the origin

Organic acids	Inorganic acids (mineral acids)
Extracted from living or organic matter.	Derived from minerals
e.g. CH3COOH, HCOOH, etc	e.g. HCl, H2SO4, HNO3 etc.

 

2.      Based on the constituent elements

Hydracids	Oxy-acids
The acids containing Hydrogen atom/s.	The acids containing Hydrogen and Oxygen atoms.
e.g. HCl, HBr, HI etc.	e.g. HNO3, H2SO4 etc.

 

3.      Based on the strength

Strong acids	Weak acids
1.      Strong acids undergo complete dissociation in their aqueous solutions H2SO4 + 2H2O   2H3O+ + SO42-   2.      give a high concentration of Hydronium ions 3.      their solutions contain ions only.   4.      These are good conductors of electricity(strong electrolytes).	1.      Weak acids undergo partial dissociation in their aqueous solutions.   CH3COOH + H2O   CH3COO- + H3O+   2.      give a low concentration of Hydromium ions 3.      their solutions contain ions and molecules. 4.      Bad conductors of electricity (weak electrolytes).

 

 

4.      Based on the Basicity of the acids

Basicity of an acid: 

The number of Hydrogen ions(protons) produced by one molecule of an acid in its aqueous solution.

Monobasic acid	Dibasic acid	Tribasic acid
One molecule of this acid produces one Hydrogen ion in its aqueous solution. e.g. HCl, HNO3, CH3COOH etc. HNO3 +H2O -->   H3O+ +NO3-	One molecule of this acid produces two Hydrogen ions in its aqueous solution. e.g. H2SO4, H2SO3 etc.   H2SO4 +2H2O --> 2H3O+ + SO42-	One molecule of this acid produces three Hydrogen ions in its aqueous solution. e.g. H3PO4   H3PO4 +3H2O-->3H3O++ PO43-