Which term refers to molar equivalents of solute per liter of solution?

• A. Molarity
• B. Molality
• C. Mass percent
• D. Normality

Answer: (D)

The concept here is how concentration is expressed in terms of reactive units rather than just amount of substance. The term that describes molar equivalents of solute per liter of solution is normality. Normality measures how many equivalents of reactive capacity are present per liter, and an equivalent depends on the reaction context (for acids, the number of protons donated; for redox, electrons transferred, etc.). So a substance can have more than one equivalent per mole, depending on how it reacts, making normality different from molarity (moles per liter) and from the other options like mass percent or molality. For example, a diprotic acid contributes two equivalents per mole when it donates protons, so 1 mole per liter would be 2 normality.