Elementary reactions ionic strength

Ionic Strength The effect of ionic strength on rates of elementary reactions readily follows. Using equation 127, we can let t>e the value of the second-order rate constant in the reference state, such as an infinitely dilute solution (where all the activity coefficients are unity) k is the rate constant at any specified ionic strength ... 

Unless otherwise indicated, the constants are presumed to be elementary reactions at T = 25 °C and zero ionic strength. Mean life times for the second-order reactions, r, are given for the case in which one of the reactants has an initial concentration (assumed to be 10 m) that is in great excess of the other. 

The primary interest in EIA is not in the mechanism of enzyme action. It is, nevertheless, essential to understand the elementary nature of enzyme reaction and of the effect of external factors, such as pH, temperature, ionic strength, other molecules and the solid-phase, on enzymic activity. For an optimal assay it is necessary to know (i) the stoichiometric details of the reaction (ii) the mole-cule(s) which should be present or avoided (iii) the kinetic dependence of the reaction on these molecules (iv) the optimization of experimental conditions and, (v) the accurate monitoring of the enzyme activity. Knowledge of the kinetic behaviour makes it possible to estimate the quantity of the immunoreactant present and to compare EIA to other assays. 

Our knowledge of these factors influencing reaction rates is quite elementary in many respects. Direct study is difficult in many instances, because of the complex nature of the hydrous metal oxide surface. Much of our current understanding comes from using indirect methods. One useful approach is to make small changes in reactant structure, then examine the effect on reaction rate. Another approach is to systematically examine how reactant concentration, medium composition (pH and ionic strength), and the presence of other adsorbing solutes influence reaction rate. 

In chemical kinetics a reaction rate constant k (also called rate coefficient) quantifies the speed of a chemical reaction. The value of this coefficient k depends on conditions such as temperature, ionic strength, surface area of the adsorbent or light irradiation. For elementary reactions, the rate equation can be derived from first principles, using for example collision theory. The rate equation of a reaction with a multi-step mechanism cannot, in general, be deduced from the stoichiometric coefficients of the overall reaction it must be determined experimentally. The equation may involve fractional exponential coefficients, or may depend on the concentration of an intermediate species. 

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