// chemistry › Concentration Units
Calculate normality N = (w×1000)/(E×V): reactive equivalents per litre, with symbol legend and real-world examples.
N = \frac{w × 1000}{E × V}
It is concentration measured in reactive equivalents per litre, instead of moles per litre. An equivalent is one unit of reacting power - one proton for an acid, one electron for a redox reaction. It tells you the solution's reactive capacity directly.
Molarity counts moles; normality counts reactive units. They link by N = M × (units per molecule). Sulfuric acid gives 2 protons, so its normality is twice its molarity - 0.05 M but 0.1 N.
It is the molar mass divided by how many reactive units each molecule provides. For H₂SO₄ (2 protons), it is 98 ÷ 2 = 49 - the value in the example. It expresses reactive capacity per gram.
Because at the endpoint, equivalents of acid equal equivalents of base: N₁V₁ = N₂V₂. That one neat relationship lets you find an unknown concentration without separately tracking protons or electrons.
Less in modern teaching (molarity is preferred), but heavily in analytical chemistry, water testing, and titration work where the equivalents idea genuinely simplifies the maths. Knowing both is a core lab skill.