It is a constant specific to a particular reaction R is gas constant and Ea is activation energy measured in joules/mole
(J mol –1) It can be understood clearly using the following simple reaction
 
 
 
2
2
H
g
I
g
2HI g


According to Arrhenius, this reaction can take place
only when a molecule of hydrogen and a molecule of iodine
collide to form an unstable intermediate (Fig 3