In order for a chemical reaction to occur there must always be

Explanation:

Molecules must collide with sufficient energy, known as the activation energy, so that chemical bonds can break. Molecules must collide with the proper orientation.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

catya that's not even a b or c