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Activation Energy

In the last lesson, we discussed how catalysts change reaction rates by decreasing the reaction's activation energy (Ea).

Eis the "energy hill" that must climbed in order to transform reactants into transition states. The type of energy that is required to stretch and position reactant bonds for activation is the activation enthalpy (ΔHa).

The terms Eand ΔHare often used interchangeably, but they are not exactly the same thing.

Ea, with units of Joules, is an intensive property of a reaction; it is an amount of potential energy.

ΔHa, with units of Joules/mole, is an extensive property of the reaction; it an amount of heat energy per mole of reactant.