Two temperature determination of Ea
At temp T1 ln (k at T1) = ln A - Ea / RT1
At temp T2 ln (k at T2) = ln A - Ea / RT2
Subtract:
ln (k at T1)  - ln (k at T2) =  - Ea (  1   -    1  )
       R  ( T1      T2 )
Or ln [(k at T1) / (k at T2)] =  - Ea (  1   -    1  )
       R  ( T1      T2 )
Knowing k at a particular temperature, and Ea
enables calculation of k at any other temperature