Arrhenius equation

The Arrhenius equation relates a reaction’s rate constant to temperature through an exponential factor containing activation energy and the gas constant. Its parameters describe how rapidly the rate changes as temperature changes.

Activation energy: The energy barrier that reacting particles must overcome for a chemical reaction to occur. It appears in the exponent and controls how strongly the rate constant responds to temperature.
Arrhenius plot: A graph of the natural logarithm of a rate constant against reciprocal absolute temperature. Its linear slope and intercept estimate activation energy and the pre-exponential factor.
Svante Arrhenius: A Swedish physical chemist who developed the theory of electrolytic dissociation and the temperature-rate relation bearing his name. He introduced the equation in the nineteenth century to describe temperature effects on reaction rates.
Modified Arrhenius equation: A rate expression that adds a power-law temperature factor to the Arrhenius exponential. It accommodates temperature dependence that a constant pre-exponential factor cannot capture.
Pre-exponential factor: A multiplicative parameter in the Arrhenius equation that captures collision frequency and the fraction of suitably oriented encounters. It sets the rate constant’s scale apart from the exponential temperature effect.
Rate constant: A proportionality constant in a rate law that quantifies reaction speed under specified conditions. The equation predicts how this quantity changes with temperature.
Chemical kinetics history: The development of methods and theories for measuring and explaining chemical reaction rates. The equation emerged as researchers sought quantitative laws for reaction speed and temperature.
Non-Arrhenius behavior: A temperature dependence of reaction rates that does not follow a single Arrhenius relationship over the range studied. Curved Arrhenius plots signal limits to the equation’s simple exponential model.
Boltzmann distribution: A probability distribution describing how energy is distributed among particles in a system at thermal equilibrium. The fraction of molecules with sufficient energy follows an exponential dependence on temperature.
Chemical reaction rate: The change in concentration of a reactant or product per unit time. A temperature-dependent rate constant translates the equation’s prediction into reaction speed.

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