Answer :
The answer is (3) heat of reaction. The difference in energy between the products and the reactants is the amount of energy either absorbed or liberated during the process (depending on whether the difference is negative or positive).
Answer: (1) activation energy
Explanation:-
Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products.
Ionization energy is the energy required to remove the most loosely bound electron from an isolated gaseous atom.
Heat of reaction is the energy released or absorbed during the course of the reaction.
Heat of vaporization is the energy required to convert 1 mole of liquid substance to gaseous form.