activity coefficient


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ac·tiv·i·ty (a),

(ak-tiv'i-tē),
1. electroencephalography The presence of neurogenic electrical energy.
See also: radioactivity.
2. physical chemistry an ideal concentration for which the law of mass action will apply perfectly; the ratio of the activity to the true concentration is the activity coefficient (γ), which becomes 1.00 at infinite dilution.
See also: radioactivity.
3. For enzymes, the amount of substrate consumed (or product formed) in a given time under given conditions; turnover number.
See also: radioactivity.
4. The number of nuclear transformations (disintegrations) in a given quantity of a material per unit time. Units: curie (Ci), millicurie (mCi), becquerel (Bq), megabecquerel (MBq).
See also: radioactivity.

activity coefficient

a proportionality constant, γ, relating activity, α, to concentration, c, expressed in the equation, α = γc.

Activity Coefficient

An idealised concentration of a solute at which the law of mass action acts in a “perfect” fashion, which can be used to determine the solute’s thermodynamic activity.

activity coefficient

1. A factor used in potentiometry to describe the activity of free ions in solution.
2. A vitamin deficiency factor that describes the enhancement of enzyme activity after saturation with a vitamin.
See also: coefficient
References in periodicals archive ?
Activity coefficients of all species are assumed to be independent of pressure.
From these possible models), (the NRTL model is selected), (because the extension of NRTL model--the polymer NRTL model--includes the effect of polymer properties on the activity coefficients of the components.
The polymer NRTL activity coefficients model interaction parameters.
iota]] is calculated from the activity coefficients predicted by the polymer NRTL model.
Because the effect of the polymer properties such as (i) chain length, (ii) molecular size, and (iii) molecule structure are not accounted on the activity coefficients in the ideal behavior modeling.
Theoretical treatments of activity coefficients in nonideal solutions have been discussed for a century.
Apparent activity coefficients of the monomer species in solution as a function of concentration are computed from van Laar coefficients of [A.
Apparent activity coefficients for the monomer species, as a function of their concentration in solution, are computed from the van Laar coefficients: [A.
Apparent activity coefficients for the pure components were computed using NRTL [26].
As such, apparent activity coefficients for lower alcohols diluted into hydrocarbon solutions are often very much greater than one.
In the absence of alcohols, physical interaction theories for nonideal behavior adequately model the activity coefficients.