What is the Equivalent Weight of Acid and Base?

Equivalent Weight:

The Equivalent Weight of an element is that part by weight of it which combines with or displaces from a compound 1.008 parts by weight of Hydrogen or 8 parts by weight of Oxygen or 35.5 parts by weight of Chlorine.

Mg + H₂SO₄ = MgSO₄ + H₂

Here, 12 parts by weight of Mg displace 1.008 parts by weight of H₂ from dil. H₂SO₄. So, the equivalent weight of Mg is 12.

Note: Equivalent Weight of an element is a pure number, it has no unit.

Equivalent Weight of Acid:

It is the quantity by weight of an acid that supplies one mole of H⁺ ion.

Equivalent Weight of an Acid = Mol. wt. of the acid / Basicity of the acid

Where,
Basicity of the acid = number of replaceable hydrogen atoms present in a molecule of the acid.

Equivalent Weight of Base:

It is the quantity by weight of a base that reacts with one mole of H⁺ ion.

Equivalent Weight of a base = Mol. wt. of the base / Acidity of the base

Where,
The acidity of the base = number of replaceable OH^– ions present in a molecule of the base.