Which term is defined as gram equivalents of solute per liter of solution?

• A. Molarity
• B. Equivalents per liter
• C. Normality
• D. Molality

Answer: (C)

Normality is the concentration unit that uses gram equivalents of solute per liter of solution. An equivalent is the amount of solute that reacts with or supplies one mole of reactive entities (such as H+ in acid–base reactions or electrons in redox reactions). So normality = equivalents per liter = (mass of solute in grams) / (equivalent weight) / liter. This differs from molarity, which uses moles per liter, and from molality, which uses moles per kilogram of solvent. The reactive capacity of the solute matters in normality, so substances like sulfuric acid give more than one equivalent per mole depending on how many protons they supply in the reaction. This makes normality especially useful in titration and reaction stoichiometry contexts.