Normality

In-depth explanation of Normality

Normality is a concentration unit defined as the number of equivalents of solute per litre of solution, N = equivalents / L. The equivalent depends on the reaction: for acids it is the number of H⁺ ions each molecule can donate, and for redox reactions it is the number of electrons transferred. Because the value depends on the reaction, normality is less precise than molarity and has largely been replaced by it. It is still used in some titration calculations and older texts. For acids and bases, normality is equal to molarity multiplied by the number of reactive groups per molecule.

Going deeper: Normality

Key ideas: Formulas: N = equivalents / L, and N = M x n, where n is the number of H+ or OH- exchanged, or electrons in a redox reaction. Neutralization at the endpoint is N1V1 = N2V2. H3PO4 is 3 N per 1 M if fully used, but may be 1 or 2 N depending on the reaction. KMnO4 is 5 N per M in acid.

Common mistakes and connections: The main mistake is using normality without specifying the reaction; the same solution has different N for different reactions. Another is using M1V1 = M2V2 for acids with different numbers of protons. IUPAC discourages normality. Links to titration, equivalent weight and redox stoichiometry.

Visualization of Normality

Normality = equivalents per litre; each mole of H2SO4 supplies 2 acid equivalents, so 1 M H2SO4 is 2 N. The interactive lesson shows this as a live animation or chart.

Worked example and use case

A 1 M solution of sulfuric acid is 2 N for acid-base reactions because each molecule can donate two protons.

Where Normality fits in States of Matter & Solutions

Normality is topic 80 of 109 in States of Matter & Solutions.

Related topics

• MolalityIntermediate
• Mass PercentBeginner
• Parts Per MillionBeginner
• DilutionBeginner
• Henry's LawIntermediate
• Temperature and SolubilityIntermediate

Browse all 109 topics in States of Matter & Solutions