Equivalent mass = molar mass ÷ n-factor
For acids: equivalent mass = molecular mass ÷ number of replaceable H⁺ ions
For bases: equivalent mass = molecular mass ÷ number of OH⁻ ions
For salts: equivalent mass = molecular mass ÷ total positive or negative charge involved in reaction
For oxidation-reduction substances: equivalent mass = molar mass ÷ number of electrons lost or gained
For metals: equivalent mass = atomic mass ÷ valency
For elements in general: equivalent mass = atomic mass ÷ combining capacity
For acids in neutralization: equivalent mass = mass of acid that supplies 1 mole of H⁺
For bases in neutralization: equivalent mass = mass of base that supplies 1 mole of OH⁻
For compounds in a given reaction: equivalent mass = mass of substance that reacts with 1 mole of H⁺, OH⁻, or electrons depending on the reaction type