Normality Calculator

Normality (N) is a measure of concentration defined as the number of gram equivalents of solute per liter of solution: N = equivalents / volume (L). An equivalent is the amount of a substance that reacts with or replaces one mole of hydrogen ions (in acid-base reactions) or one mole of electrons (in redox reactions). N = Molarity * n-factor, where n-factor is the number of equivalents per mole.

The n-factor (equivalence factor) is the number of equivalents per mole of substance. For acids: n-factor = number of replaceable H+ ions (HCl = 1, H2SO4 = 2, H3PO4 = 3). For bases: n-factor = number of OH- ions provided (NaOH = 1, Ca(OH)2 = 2). For redox: n-factor = change in oxidation state per formula unit (KMnO4 in acidic solution = 5, in neutral = 3, in alkaline = 1).

N = M * n-factor, where M is molarity (mol/L) and n-factor is the number of equivalents per mole. For H2SO4 (n-factor = 2): a 1 M solution is 2 N. For NaOH (n-factor = 1): 0.5 M = 0.5 N. Conversely, M = N / n-factor. In acid-base titrations at the equivalence point: N1V1 = N2V2 (exactly, regardless of the specific acid or base).

IUPAC recommends using molarity because normality depends on the reaction context: the n-factor of H3PO4 is 1, 2, or 3 depending on which proton is being replaced. Normality is ambiguous for such polyprotic acids. Modern analytical chemistry generally prefers molarity for this reason, though normality remains common in industrial water treatment, clinical labs, and some educational contexts.

Gram equivalent weight = Molar mass / n-factor. For H2SO4 (MM = 98 g/mol, n = 2): equivalent weight = 49 g/equiv. One gram equivalent of any acid neutralizes exactly one gram equivalent of any base. To prepare 1 N H2SO4: dissolve 49 g of H2SO4 per liter of solution. This is the practical significance of normality in stoichiometric calculations.