The rate of most reactions changes with temperature because the rate constant
k varies with temperature. Arrhenius established experimentally the relationship between rate constant
k and the temperature (
T) in Kelvin shown at the left below.
for a particular reaction
A, the preexponential factor, is constant
R is the ideal gas constant
Ea, the activation energy, is constant
k = Ae-Ea/RT
If the rate constant at several temperatures is known the Arrhenius equation shown can be used to determine the activation energy for a reaction .
| ln k | = | – | Ea | × | 1 | + ln A |
| R | T |
|||||||
| y | = | | m | | x | + c |
This is because the logarithmic form of the equation shows that there is a linear relationship between ln
k and 1/
T. Thus a plot of
ln k vs 1/T is a straight line with the slope –
Ea/
R where
R is the gas constant.