activity coefficient

Also found in: Dictionary, Thesaurus, Legal, Financial, Encyclopedia, Wikipedia.

ac·tiv·i·ty (a),

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 ?
In the absence of alcohols, physical interaction theories for nonideal behavior adequately model the activity coefficients.
71-co-AN), such as the glass transition temperature, Tg; the sorption enthalpy, IH 1S, sorption free energy, IG 1S; sorption entropy, IS 1S; the weight fraction activity coefficients, a| 1a; partial molar free energy of mixing, IG 1a; partial molar heat of mixing, IH 1a; and the Flory-Huggins interaction parameters, I 12a, at infinite dilution.
As a consequence, the sorption parameters and the solvent activity coefficients and the Flory Huggins parameters were calculated only in the temperature range from 60 to 80[degrees]C and for polar-type and dispersion-type solvents in whose retention diagrams this decreasing linear zone can be clearly observed.
Henry's constants and infinite dilution activity coefficients of propane, propene, butane, isobutane, 1-butene, isobutene, trans-2-butene, and 1,3-butadiene in 1-butanol and 2-butanol from (250 to 330) K.
2/kmol amine [gamma] activity coefficient [psi] objective function for regression Subscripts a, X anion c, M cation n,n' neutral solvent species cal calculated value ex experimental value s solvent i ionic or neutral solute w water solvent
The activity coefficients and other thermodynamic properties of hydrochloric acid are dependent not upon the value of E[degrees] but on the difference E-E[degrees].
Similarly, in absence of any coupling effect between i and j (State II) activity coefficient of component i or j in membrane is obtained using Flory--Huggins thermodynamics, that is,
The weight fraction activity coefficient, 1, and Flory-Huggins interaction parameter are important for defining solvent-polymer interactions.
The selection of the activity coefficient model is crucial to reliably predict the activity coefficients.
This chapter gives a consistent and axiomatic approach to fluid thermodynamics; it avoids using activity coefficients.