What is the equivalent weight of KMnO4?

The equivalent weight of KMnO₄ (potassium permanganate) depends on the medium of the reaction because its valency changes in different conditions.

Formula:
Equivalent weight = Molecular weight / n-factor

Where n-factor is the number of electrons gained or lost per molecule.

Molecular Weight of KMnO₄:
= 39 (K) + 55 (Mn) + 64 (O₄) = 158 g/mol

1. In Acidic Medium:

• Mn changes from +7 to +2 (gain of 5 electrons)
• n-factor = 5

Equivalent weight = 158 / 5 = 31.6 g/equiv

1. In Neutral Medium:

• Mn changes from +7 to +4 (MnO₂ formed)
• n-factor = 3

Equivalent weight = 158 / 3 ≈ 52.67 g/equiv

1. In Alkaline Medium:

• Mn changes from +7 to +6
• n-factor = 1

Equivalent weight = 158 / 1 = 158 g/equiv

Conclusion:
The equivalent weight of KMnO₄ varies with the reaction medium:

• Acidic: 31.6 g/equiv
• Neutral: 52.67 g/equiv
• Alkaline: 158 g/equiv