Question

Describe how one calculates the energy of activation for a reaction.

Answer 1

Activation energy may be defined as the minimum amount of energy must be given to the reactants to start the reaction.

Activation energy of the reaction can be calculated from the threshold energy and enthalpy of the reactants.

Threshold energy is the minimum energy must be possessed by the reactants to participate in chemical reaction. Enthalpy of the reactants is the energy possessed by the molecules (reactants).

Therefore Activation energy = Threshold energy - enthalpy of reactants.

In another way activation energy can be calculated from the known values of rate constants at two different temperatures by using Arrhenius equation.