Arrheniusplottet

Arrheniusplottet, commonly known as the Arrhenius plot, is a graphical method used in chemical kinetics to analyze how reaction rates depend on temperature. It plots the natural logarithm of the rate constant k against the reciprocal of the absolute temperature 1/T (in kelvin). According to the Arrhenius equation k = A exp(-E_a/(R T)), the plot is linear if the mechanism remains unchanged over the temperature range, with the slope equal to -E_a/R and the intercept equal to ln A. If a base-10 logarithm is used, the slope is -E_a/(2.303 R). From the slope and intercept, the activation energy E_a and the pre-exponential factor A can be determined.

The Arrhenius plot is widely used across fields such as gas-phase kinetics, solution chemistry, solid-state reactions, electrochemistry, catalysis, corrosion studies, and battery materials. It provides a simple visual check of whether a reaction follows simple Arrhenius behavior and allows quick comparison of kinetic parameters between different systems or catalysts.

Limitations and interpretation caveats are important. Real systems may deviate from linearity due to changes in mechanism with temperature, multiple reaction steps, diffusion limitations, or phase transitions. Activation energy themselves can be temperature-dependent. At low temperatures, quantum tunneling can also cause departures from Arrhenius behavior. Therefore, linearity should be assessed over an appropriate temperature range where the mechanism is believed to be constant, and data quality and experimental conditions should be carefully considered.