Graph that shows the logarithmic rate of heat production ln(q) versus the inverse temperature (l/T) in Kelvin. This results in a straight line with a gradient -Ea/R for single, non-autocatalyzed reactions. Autocatalysis results in typical deviations of the straight line. In practice, the rate of reaction is often affected by physical processes (e.g. diffusion), which results in the occurrence of an apparent activation energy.