equilibrium constant


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e·qui·lib·ri·um con·stant (Keq),

in the reaction A + B ⇄ C + D at equilibrium (that is, no net change in concentrations of A, B, C, or D), the concentrations of the four components are related by the equation Keq = [C][D]/[A][B]; Keq is the equilibrium constant If any component in the reaction has a multiplier (for example, H2 ⇄ 2H), that multiplier appears as an exponent in the calculation of K (for example, Keq = [H]2/[H2]). When this equation is applied to the ionization of a substance in solution, Keq is called the dissociation constant (Kd) and its negative logarithm (base 10) is the pKd.
See also: Henderson-Hasselbalch equation, mass:action ratio.
References in periodicals archive ?
Table 1 lists the equilibrium constants together with their standard deviations as obtained from the program MINIQUAD-75.
In a second step of this study, using the Painter-Coleman association model, the equilibrium constants describing both the self-association [K.sub.2] and interassociation [K.sub.A] and the enthalpy of hydrogen bonding formation in the different blends were experimentally determined using appropriate curve fitting analysis of the infra-red spectra as a function of temperature.
Rate and equilibrium constants for the reactions of alkoxysilanes with monosolvated alkylmagnesium chlorides in toluene at 20[degrees]C Silane Grignard reagent K, L x [mol.sup.-1] [Si(OEt).sub.4] n-BuMgCl x [Bu.sub.2]O 2.24 [+ or -] 0.06 n-BuMgCl x [Et.sub.2]O 1.22 [+ or -] 0.02 n-BuMgCl x THF 0.40 [+ or -] 0.02 i-PrMgCl x [Et.sub.2]O 2.40 [+ or -] 0.02 [i-PrSi(OEt).sub.3] n-BuMgCl x [Et.sub.2]O 0.8 [+ or -] 0.2 Grignard reagent k, [s.sup.-1] Method n-BuMgCl x [Bu.sub.2]O 0.20 [+ or -] 0.02 B n-BuMgCl x [Et.sub.2]O 0.31 [+ or -] 0.01 B n-BuMgCl x THF 0.12 [+ or -] 0.03 A i-PrMgCl x [Et.sub.2]O (1.17 [+ or -] 0.04) x [10.sup.-3] A n-BuMgCl x [Et.sub.2]O (2.2 [+ or -] 0.4) x [10.sup.-3] A
Physical interactions among polymer functional groups are represented with traditional [chi] parameters, while Chemical interactions are represented with equilibrium constants.
[k.sub.s] is the equilibrium constant of reaction s and [[c.sub.k]] is the molar concentration of species k.
Because the H:C ratio of methanol is over double that of gasoline, it was predicted that D-EGR [H.sub.2] reformate yield could more than double, based on the WGS equation and equilibrium constant of gasoline.
If the rates of association and dissociation between the compound and binding agent are relatively fast compared to the time the compound spends in the column, the values of [t.sub.R] and k will depend on both the number of binding sites for this compound in the column and equilibrium constants for these sites (8).
TABLE 1: Parameters of [H.sub.2]O equilibrium constant in (6).
The equilibrium constant [K.sub.eq2] for Equation (2) was calculated from the simulated equilibrium composition for the OS ash-water model systems (Fig.
The free energy of reaction ([DELTA][G.sup.o]r) at standard state is related to the equilibrium constant (K) in the following equation:
The first is the equilibrium constant ([K.sub.eq] = [k.sub.a]/[k.sub.da]) of the atom transfer reaction, which determines the concentration of active radicals propagating at any time in the reaction.

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