Consider the following reaction: H2(g) + I2 (g) 2HI(g)
The activation energy for this reaction is 169 kJ/mol. ΔE for this reaction is +27 kJ/mol.
Activity energy is the minimum energy required by the reactants to occur the reaction.
AE is the energy difference between products and reactants. It is also obtained as the difference between activation energies of forward and reverse reactions.
Decomposition of HI (g) is the reverse reaction of given reaction. Calculate the activation energy for reverse reaction as follows:
ΔE = activation energy of forward reaction - activation energy of reverse reaction +27 kJ/mol = 169 kJ/mol - activation energy of reverse reaction
Activation energy of reverse reaction =169 kJ/mol - 27 kJ/mol = 142 kJ/mol
Therefore, the activation energy for the decomposition of HI = 142 kJ/mol