Normality from Molarity

Normality counts reactive capacity rather than molecules. One mole of sulfuric acid delivers two protons, so 0.500 M H₂SO₄ is 1.00 N — and 1.00 N of any acid neutralises 1.00 N of any base volume for volume, which is exactly why the unit survived so long in analytical labs. For redox work the equivalents are electrons: potassium permanganate in acid picks up five, making 0.0200 M KMnO₄ a 0.100 N oxidant.

The catch, and the reason IUPAC deprecated normality decades ago, is that the equivalent count depends on the reaction, not the substance. Phosphoric acid is 3 N when fully neutralised to phosphate but only 1 N in a titration stopped at the first endpoint, so a bottle labelled "1 N H₃PO₄" is ambiguous without knowing the intended reaction. You will still meet it constantly in water-treatment and clinical chemistry, where hardness, alkalinity, and electrolyte balances are quoted in equivalents per litre or milliequivalents per litre — blood sodium at 140 mEq/L being the most familiar example.