Activation Energy
For users of the Mathcad browser: wmc-re1.mcd (8 KB, ver. 5.0)The rate constant is a function of
the temperature and can be calculated from the Arrhenius
equation:
The same
formula can be used to calculate the activation energy Ea from a
set of experimentally determined rate constants at different
temperatures.
For example, in the hydrolysis of
2-chloro-2-methylpropane, the following data was obtained:
| T/K | 303 |
298 | 293 | 288 | 283 |
| k*10^2 | 9.41 | 3.59 | 3.08 | 2.44 |
1.82 |
The exponential
equations can be converted to the linear form by taking the logarithm of
both sides, which in our case would give: 
Plotting lnk against 1/T should give an
approximately straight line relationship
with a slope, Ea/R and an intercept, lnA. In this case
the calculations involve the lnk values instead of the plain
k values, and the reciprocal values of the temperature.
« Home » « Mathcad Menu »
Plotting lnk against 1/T should give an
approximately straight line relationship
with a slope, Ea/R and an intercept, lnA. In this case
the calculations involve the lnk values instead of the plain
k values, and the reciprocal values of the temperature.