Which term describes solute concentration as gram equivalents per liter of solution?

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

Answer: (A)

Normality expresses solute concentration as gram equivalents per liter of solution. An equivalent is the amount of substance that reacts with or supplies one mole of reactive units (such as H+, OH−, or electrons) in a given reaction. So normality = equivalents per liter (N = Eq/L). This means the same substance can give different normalities in different reactions depending on how many reactive units it provides; for example, one mole of HCl yields one equivalent, while one mole of H2SO4 yields two equivalents of H+. Consequently, 1 M HCl is 1 N, but 0.5 M H2SO4 is also 1 N. Molarity measures moles per liter, not equivalents; molality uses moles per kilogram of solvent. While “equivalents per liter” is a descriptive phrase, the standard term for this concept is normality.