ქიმიის ტერმინთა განმარტებითი ლექსიკონი

The standard enthalpy of activation Δ^‡H° is the enthalpy change that appears in the thermodynamic form of the rate equation obtained from conventional transition state theory. This equation is only correct for a first order reaction, for which the rate constant has the dimension reciprocal time. For a second order reaction, for which the rate constant has the dimension (reciprocal time) × (reciprocal concentration), the left hand side should be read as kc° , where c° denotes the standard concentration (usually 1 mol dm^-3).

The quantity Δ^‡S° is the standard entropy of activation, and care must be taken with standard states. In this equation k_B is the Boltzmann constant, T the absolute temperature, the h Planck constant, and R the gas constant. The enthalpy of activation is approximately equal to the activation energy; the conversion of one into the other depends on the molecularity. The enthalpy of activation is always the standard quantity, although the word standard and the superscript on the symbol are often omitted.

The symbol is frequently (but incorrectly) written ΔH^‡, where the standard symbol is omitted and the ‡ is placed after the H.