N = M × n (equivalents per mole)
Normality (N) is concentration expressed in gram equivalents per liter. N = M × n, where M is molarity and n is the number of equivalents per mole — this depends on the reaction context. For acid-base: n = number of H⁺ or OH⁻ per formula (HCl: n=1, H₂SO₄: n=2, H₃PO₄: n=3). For redox: n = electrons transferred per formula unit (KMnO₄ in acid: n=5 because Mn goes from +7 to +2). The advantage of normality: at the equivalence point, NₐVₐ = NbVb always works regardless of the reaction stoichiometry. The equivalent weight = molar mass/n. While IUPAC discourages normality in favor of molarity, it remains widely used in clinical chemistry, water treatment, and titration-heavy analytical methods.