Concentration equilibrium constant

K,K, equilibrium constant (concentration basis v = stoichiometric number) (mol L ) "... 

Adsorption equilibrium constant Concentration equilibrium constant Equilibrium constant (dimensionless)... 

Kp, K, equilibrium constant concentration of gas expressed in terms of pressure (P) and molarity (M), respectively... 

Ludwig, Chr. GRIFIT, A Program for Solving Speciation Problems Evaluation of Equilibrium Constants, Concentrations and other Physical Parameters, Internal Report, University of Berne, 1992. 

The dissociation constant for CH3COOH at 25 °C is from Appendix D addition of CH3COONa does not change the value of this constant. Substituting the equilibrium-constant concentrations from our table into the equilibrium expression gives ... 

Apparent equilibrium constant (concentration ratio) Thermodynamic equilibrium constant (activity ratio)... 

We recall that the (practical) equilibrium constant (concentration ratio) is given by K=kjk . Thus we may formally express K of ionic (-dipolar) equilibria of the type (2.13) by... 

On the other hand, hydrogen present in liquid is rapidly consumed and because of mass transfer it reduces its concentration. In the next section of the reactor, the easiness of hydrogen sulfide transfer and hydrogen concentration in liquid phase increase gradually from liquid to gas phase by the effect of equilibrium. Constant concentration of these compounds is expected at the last part of catalytic bed supposing equilibrium, but in the experimental reactor it does not seem to occur. 

One can write acid-base equilibrium constants for the species in the inner compact layer and ion pair association constants for the outer compact layer. In these constants, the concentration or activity of an ion is related to that in the bulk by a term e p(-erp/kT), where yp is the potential appropriate to the layer [25]. The charge density in both layers is given by the algebraic sum of the ions present per unit area, which is related to the number of ions removed from solution by, for example, a pH titration. If the capacity of the layers can be estimated, one has a relationship between the charge density and potential and thence to the experimentally measurable zeta potential [26]. 

A connnon approach has been to measure the equilibrium constant, K, for these reactions as a fiinction of temperature with the use of a variable temperature high pressure ion source (see section (Bl.7.2)1. The ion concentrations are approximated by their abundance in the mass spectrum, while the neutral concentrations are known from the sample mlet pressure. A van t Hoff plot of In K versus /T should yield a straight Ime with slope equal to the reaction enthalpy (figure B1.7.11). Combining the PA with a value for basicityG at one temperature yields a value for A.S for the half-reaction involving addition of a proton to a species. While quadnipoles have been tire instruments of choice for many of these studies, other mass spectrometers can act as suitable detectors [19, 20]. 

Figure B2.5.7 shows the absorption traces of the methyl radical absorption as a fiinction of tune. At the time resolution considered, the appearance of CFt is practically instantaneous. Subsequently, CFl disappears by recombination (equation B2.5.28). At temperatures below 1500 K, the equilibrium concentration of CFt is negligible compared witli (left-hand trace) the recombination is complete. At temperatures above 1500 K (right-hand trace) the equilibrium concentration of CFt is appreciable, and thus the teclmique allows the detennination of botli the equilibrium constant and the recombination rate [54, M]. This experiment resolved a famous controversy on the temperature dependence of the recombination rate of methyl radicals. Wliile standard RRKM theories [, ] predicted an increase of the high-pressure recombination rate coefficient /r (7) by a factor of 10-30 between 300 K and 1400 K, the statistical-adiabatic-chaunel model predicts a...

Equilibrium constants for protein-small molecule association usually are easily measured with good accuracy it is normal for standard free energies to be known to within 0.5 kcal/mol. Standard conditions define temperature, pressure and unit concentration of each of the three reacting species. It is to be expected that the standard free energy difference depends on temperature, pressure and solvent composition AA°a also depends on an arbitrary choice of standard unit concentrations. 

The equilibrium constants obtained using the metal-ion induced shift in the UV-vis absorption spectrum are in excellent agreement with the results of the Lineweaver-Burke analysis of the rate constants at different catalyst concentrations. For the copper(II)ion catalysed reaction of 2.4a with 2.5 the latter method gives a value for of 432 versus 425 using the spectroscopic method. 

Measurements were performed employing a Perkin Elmer X2, 5 or 12 UV-Vis spectrophotometer at 25 O.r- C. Equilibrium constants were determined by measuring the extinction coefficient at a suitable wavelength of the partially complexed dienophile (y,.hs) as a function of the concentration of... 

Numerous attempts to determine the equilibrium constants using titration microcalorimetry failed, due to solubility problems encountered at the higher concentrations of catalyst and dienophile that are required for this technique. 

The equilibrium constant K, the rate constants and and the dependences of all these quantities on temperature were determined. In the absence of added acetic acid, the conversion of nitric acid into acetyl nitrate is almost quantitative. Therefore, to obtain at equilibrium a concentration of free nitric acid sufficiently high for accurate analysis, media were studied which contained appreciable concentrations (c. 4 mol 1 ) of acetic acid. 

The acid dissociation constant has the same form m Brpnsted-Lowry as m the Arrhenius approach but is expressed m the concentration of H30" rather than The concentration terms [H30" ] and [H" ] are considered equivalent quantities m equilibrium constant expressions... 

Even though water is a reactant (a Brpnsted base) its concentration does not appear m the expression for because it is the solvent The convention for equilibrium constant expressions is to omit concentration terms for pure solids liquids and solvents... 

Analytical chemistry is inherently a quantitative science. Whether determining the concentration of a species in a solution, evaluating an equilibrium constant, measuring a reaction rate, or drawing a correlation between a compound s structure and its reactivity, analytical chemists make measurements and perform calculations. In this section we briefly review several important topics involving the use of numbers in analytical chemistry. 

For a reaction at equilibrium, the equilibrium constant determines the relative concentrations of products and reactants. 

The equilibrium position for any reaction is defined by a fixed equilibrium constant, not by a fixed combination of concentrations for the reactants and products. This is easily appreciated by examining the equilibrium constant expression for the dissociation of acetic acid. 

Most reactions involve reactants and products that are dispersed in a solvent. If the amount of solvent is changed, either by diluting or concentrating the solution, the concentrations of ah reactants and products either decrease or increase. The effect of these changes in concentration is not as intuitively obvious as when the concentration of a single reactant or product is changed. As an example, let s consider how dilution affects the equilibrium position for the formation of the aqueous silver-amine complex (reaction 6.28). The equilibrium constant for this reaction is... 

Count the number of species whose concentrations appear in the equilibrium constant expressions these are your unknowns. If the number of unknowns equals the number of equilibrium constant expressions, then you have enough information to solve the problem. If not, additional equations based on the conservation of mass and charge must be written. Continue to add equations until you have the same number of equations as you have unknowns. 

Besides equilibrium constant equations, two other types of equations are used in the systematic approach to solving equilibrium problems. The first of these is a mass balance equation, which is simply a statement of the conservation of matter. In a solution of a monoprotic weak acid, for example, the combined concentrations of the conjugate weak acid, HA, and the conjugate weak base, A , must equal the weak acid s initial concentration, Cha- ... 

Substituting equations 6.39 and 6.40 into the equilibrium constant expression for the dissociation of HE (equation 6.35) and solving for the concentration of H3O4 gives us... 

Since the concentrations of Na+, A-, HA, H3O+, and OH- are unknown, five equations are needed to uniquely define the solution s composition. Two of these equations are given by the equilibrium constant expressions... 

Since the equilibrium constant for this reaction is large, we may treat the reaction as if it went to completion. The new concentrations of NH4+ and NH3 are therefore... 

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