Activation Energy

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Equation / Last modified by Administrator on 2015/06/09 07:08
`E_a = `
vCalc.Activation Energy

The activation energy, `E_a`, is the minimum energy molecules must possess in order to form a product. In other words, the activation energy is the minimum energy that must be input to an amount of chemical reactants to cause a chemical reaction.

The activation energy can be found algebraically by substituting two rate constants (k1, k2 in units of 1/mole) and the two corresponding reaction temperatures (T1, T2) into the Arrhenius Equation.1 The reault is expressed typically in kJ/mol.

original author: Juliet


Activation Energy - is a term introduced in 1889 by the Swedish scientist Svante Arrhenius that is defined as the energy that must be overcome in order for a chemical reaction to occur. Activation energy may also be defined as the minimum energy required to start a chemical reaction.

The velocity, and correspondingly the kinetic energy, of gas molecules increase with increasing temperatures. Liquids and solids exhibit the same temperature dependent increase in energy, so most chemical reaction are affected by temperature..   The higher kinetic energy of molecules with temperature means that the minimum energy to cause a reaction can be reached by raising the temperature of the reacting components, thus lowering the activation energy.  The Activation Energy equation represents the temperature dependence of this threshold for a chemical reaction.

Activation energy represents the height of the potential energy barrier. For a chemical reaction to commence, an appreciable amount of the reactants must exist with energy equal to or greater than the activation energy.

The Arrhenius activation energy term from the Arrhenius equation is an experimentally determined parameter that indicates the sensitivity of the reaction rate to temperature.  The portion of the molecules required to exceed the activation threshold, `E_a`, is defined by a related equation, the Arrhenius Equation.