No, it is not possible for a reaction to have zero activation energy. Activation energy is the minimum amount of energy required for a chemical reaction to occur. It represents the energy barrier that must be overcome for reactant molecules to reach the transition state and form products.
According to the principles of thermodynamics and kinetics, all chemical reactions require some level of activation energy to proceed. The activation energy is needed to break the existing bonds in the reactant molecules and initiate the formation of new bonds in the product molecules.
Even highly exothermic reactions that release a large amount of energy still have an activation energy requirement. The exothermicity of a reaction indicates that the products are at a lower energy level than the reactants, but it doesn't eliminate the need for an initial energy input to initiate the reaction.
In some cases, catalysts can lower the activation energy of a reaction by providing an alternative reaction pathway with a lower energy barrier. However, even with a catalyst, there is still an activation energy associated with the reaction.
Therefore, all chemical reactions require a minimum amount of activation energy, and it is not possible for a reaction to have a zero activation energy.