Relationship between activation energy and temperature

Arrhenius Equation: $\ln k = - \frac{E_{a}}{RT} + \ln A$

rachelmackenzie3H
Posts: 10
Joined: Fri Jul 22, 2016 3:00 am

Relationship between activation energy and temperature

If the activation energy for a reaction is independent of temperature, how come we have the equation Ea= delta H + RT? Wouldn't an increase in temp cause an increase in the Ea?

Jessica Huang 1M
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

Re: Relationship between activation energy and temperature

Ea= deltaH + RT is just an approximation. To find the actual Ea, (deltaG of activation)= (deltaH of activation) -T(deltaS of activation). But, in practice the deltaG equation is difficult to use because it's difficult to know what the activated complex is. Therefore, in reality, one would use Ea= deltaG of activation= deltaH of activation + RT. We can use the approximation because RT is pretty much always greater than TdeltaS.

An increase in temperature would not cause an increase in Ea. Ea is the energy that molecules must overcome in order to become products. Increasing the temperature would increase the energy of the molecules, giving them enough energy to overcome Ea.