Activity coefficients

Activity coefficients measure how the behavior of a substance in a mixture differs from that of a pure substance. In ideal conditions, particles don't affect each other, and their activity equals their concentration. However, in real mixtures, interactions like attraction or repulsion cause deviations, meaning the substance's effective "quantity"—its activity—is different from its actual amount. The activity coefficient quantifies this deviation; a value of 1 indicates ideal behavior, while values above or below 1 reflect stronger or weaker interactions, respectively. Understanding activity coefficients helps predict and control how substances behave in solutions, especially in chemistry, engineering, and related fields.