Threshold energy ( ET ) The minimum amount of energy which the reactant must possess in order to convert into products is known as threshold energy .
Activation energy ( Ea ) The additional amount of energy , required by the reactant so that their energy becomes equal to the threshold value is known as activation energy .
⇒ Ea = ET – ER
Lower the activation energy , faster is the reaction .
Different reactions have different rates because their activation energies are different .
Larger the value of Eo , smaller the value of rate constant and greater is the effect of a given temperature rise on K
Important points about Arrhenius equation ( i ) If R2 and R1 are rate constant at temperature T2 and T1 ; then
ii ) Fraction of molecules with energy equal to or greater than the activation energy is called Boltzmann factor and is given by
( ii ) Ea is constant for a particular reaction .
( iii ) Ea does ’ t depend on temperature , volume , pressure , etc ., but gets affected by catalyst .