An activity coefficient is a factor used in thermodynamics to account for deviations from ideal behaviour in a mixture of chemical substances. In an ideal mixture, the interactions between each pair of chemical species are the same (or more formally, the enthalpy of mixing is zero) and, as a result, properties of the mixtures can be expressed directly in terms of simple concentrations or partial pressures of the substances present e.g. Raoult's law. Deviations from ideality are accommodated by modifying the concentration by an activity coefficient. Analogously, expressions involving gases can be adjusted for non-ideality by scaling partial pressures by a fugacity coefficient.
The concept of activity coefficient is closely linked to that of activity in chemistry.
Read more about Activity Coefficient: Thermodynamics, Application To Chemical Equilibrium, Measurement and Prediction of Activity Coefficients
Famous quotes containing the word activity:
“The superstition respecting power and office is going to the ground. The stream of human affairs flows its own way, and is very little affected by the activity of legislators. What great masses of men wish done, will be done; and they do not wish it for a freak, but because it is their state and natural end.”
—Ralph Waldo Emerson (1803–1882)