Reaction rate constant

In chemical kinetics a reaction rate constant k or λ quantifies the speed of a chemical reaction.

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For a chemical reaction n A + m B → C + D, the reaction rate is typically of the form

Here [X] denotes, for a reaction between liquids, gases, or solutes, the concentration of X; for a reaction taking place at a boundary it would denote something like moles of X per area.

In this equation k(T) is the reaction rate constant that depends on temperature.

The exponents n' and m' are called orders and depend on the reaction mechanism. In a single-step reaction can also be written as

E_a is the activation energy and R is the Gas constant. Since at temperature T the molecules have energies according to a Boltzmann distribution, one can expect the proportion of collisions with energy greater than E_a to vary with e^-Ea/RT. A is the pre-exponential factor or frequency factor.

The Arrhenius equation gives the quantitative basis of the relationship between the activation energy and the reaction rate at which a reaction proceeds.

See also

Reaction rate