# Activity Coefficient

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

### Other articles related to "activity coefficient, activity coefficients, activity":

Debye–Hückel Theory - Mathematical Development
... symmetrical electrolyte, in terms of the mean activity coefficient is given as I is the ionic strength and a0 is a parameter which represent the ... most significant aspect of these algebraic manipulations is the prediction that the mean activity coefficient is a function of ionic strength ... Generally, activity coefficients are discussed in terms of ionic strength rather than the electrolyte concentration ...
Debye–Hückel Equation - Debye-Hückel Limiting Law
... equation see Debye-Hückel theory In order to calculate the activity of an ion in a solution, one must know the concentration and the activity coefficient ... The activity of some ion species C, is equal to a dimensionless measure of the concentration of C, multiplied by the activity coefficient of C ... The Debye-Hückel limiting law enables one to determine the activity coefficient of an ion in a dilute solution of known ionic strength ...
Measurement and Prediction of Activity Coefficients
... Activity coefficients may be measured experimentally or calculated theoretically, using the Debye-Hückel equation or extensions such as Davies equation, Pitzer equations or TCPC model ... A new alternative for activity coefficients prediction, which is less dependent on model parameters, is the COSMO-RS method ... For uncharged species, the activity coefficient γ0 mostly follows a "salting-out" model This simple model predicts activities of many species (dissolved undissociated ...
Total Ionic Strength Adjustment Buffer - Theory
... The activity of a substance in solution depends on the product of its concentration and the activity coefficient in that solution ... The activity coefficient depends on the ionic strength of the solution in which the potentiometric measurements are made ... In most cases, the analyst's goal is simply to make sure that the activity coefficient is constant across a set of solutions, with the assumption that no ...

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Barbara Coloroso (20th century)