In chemistry, what does the word Normality mean?

Normality is a way of expressing concentration specifically in terms of equivalent weights of a solute per liter of solution. When we refer to a solution's normality, we essentially quantify how many equivalents of a reactive species are present in a given volume of solution. This is particularly useful in acid-base chemistry and redox reactions, where the reactivity often depends on the number of equivalents rather than just moles of solute.

For instance, in the case of an acid, one equivalent would correspond to the amount of acid that can donate one mole of protons (H⁺ ions). Therefore, understanding normality allows chemists to tailor solution concentrations according to the specific reactions they are conducting.

Other definitions such as percentage of a solute, moles of solute per liter, or mass of solute per volume represent different ways to express concentration, but they do not adequately encapsulate the concept of equivalent weight, which is central to the definition of normality. Thus, the focus on equivalent weights per liter distinguishes normality from other concentration measures in chemistry.