Rate constant of reaction can be expressed by Arrhenius equation as,
In this equation, E represents:
(a) the energy above which all the colliding molecules will react
(b) the energy below which colliding molecules will not react
(c) the total energy of the reacting molecules at a temperature, T
(d) the fraction of molecules with energy greater than the activation energy of the reaction
(b) E is activation energy. If Ea + iR = Ethreshhold energy, then only molecules may react.