The speed of a chemical reaction is based on the height of the activation energy. Now here activation energy which is your energy barrier and abbreviated as EA equals your transition state. So abbreviate as TS minus you'll reactant line. So we're going to say here, if we're to look at these two energy diagrams, remember this is your transition state, this is your reactant, this is your transition state, this is your reactant.

From this we could calculate the energy of activation for both of these curves. So if we were to do that, we'd say that the transition state up here looks like it's around 90, so this would be 90. And then the reactant line looks like it touches 20, so this would be 70 kilojoules for the activation energy. So remember, it's the difference between the two. And then in our other curve, the transition state looks like it's 60 and the reactant line still looks like it's around 20. So that's 40 kilojoules. So remember it's the difference between the two which represents our activation energy.

Now what's important here, we're going to say that the higher the activation energy, then fewer reactive molecules have enough energy to convert into products. So we're going to say here a higher activation energy equates to a slower reaction and a smaller activation energy equates to a faster reaction. Here we just calculated the activation energy for two energy diagrams, this one being 70 kilojoules and this one being 40.

So remember the one that has the higher activation energy would represent our slower reaction and the one that has the smaller or lower activation energy would represent arc faster reaction. So just remember we can use activation energy to give us a good idea of how quickly or how slowly any typical chemical reaction will go. So keep this in mind when calculating activation energy.