Reaction rate constant

The rate constant, the symbol. It is used in chemistry to the proportionality of the reaction rate to the concentration of two substances A and B in the equation


In the calculation of the rate constants k ( according to the Arrhenius equation ) Go the frequency factor A (or pre-exponential factor called ), the activation energy (unit: J / mol), the universal gas constant R ( = 8.314 J / ( K mol) ) and the absolute temperature T ( in Kelvin K) a:

Empirical Arrhenius equation assumes that the frequency factor A is not dependent on temperature, which is sufficiently accurate for most needs approximation. From the collision theory, however, a equation derives that takes into account the temperature dependence of the frequency factor A.

The frequency factor A corresponds to the product of the collision frequency Z and the orientation factor P. The frequency factor A is thus the maximum number of collisions in the gas phase, while respecting the need for the reaction orientation of the molecules to.

The unit of the rate constant depends on the reaction order and follows the general formula wherein the reaction order equal.