Question

In the arrhenius equation, `k = Ae^(-E_a"/"RT)`, what is the frequency factor?

Answer 1

In collision theory, a major proposition is that a successful collision (overcoming the activation energy `E_a`) gives you a successful reaction.

The frequency factor is `A`, also known as the pre-exponential factor. This is essentially an experimentally-acquired constant.

It generally represents the frequency of collisions between molecules in a reaction. It is the fraction of molecules that would react if there existed no energy barrier. Here's why.

The Arrhenius equation is:

`\mathbf(k = Ae^(-E_a"/"RT))`

But if there were no energy threshold, above which the reaction can occur, then the activation energy `E_a = 0`.

Thus, `e^(-E_a"/"RT) = e^0 = 1`, and:

`color(green)(k = A)`

So, the higher `A` is for a specific reaction, the more frequent collisions would be observed for that reaction, and thus we would see the reaction successfully occur more easily.

NOTE: Although `A` is temperature-dependent, if we choose a small-enough temperature range, we can assume that `A` is constant for two reactions at different temperatures.