# How do you find A in Arrhenius equation?

##### 1 Answer

Plot a graph of

#### Explanation:

The Arrhenius equation is

#k = A e^{-E_"a"/(RT)}# ,

where

This can be rewritten as

#ln(k) = ln(A) - E_"a"/R * 1/T#

If you measured the rate constant,

#ln(k_1) = ln(A) - E_"a"/R * 1/T_1#

#ln(k_2) = ln(A) - E_"a"/R * 1/T_2#

Solve them simultaneously and you will get

#E_"a" = frac{Rln(k_2/k_1)}{1/T_1 - 1/T_2}#

#A = e^{frac{T_2ln(k_2) - T_1ln(k_1)}{T_2 - T_1}}#

If you measured the rate constant at many different temperatures, you can plot a graph of

Extrapolate and get the