WAEC Chemistry 2017 Paper

Concept:For a chemical reaction to occur, reactant particles must collide with sufficient energy.Explanation:Chemical reactions happen only when colliding molecules possess at least the minimum energy required to break existing bonds.This minimum energy is called the activation energy, $E_a$.If the energy of the colliding reactants is less than $E_a$, the collision is ineffective and no reaction occurs.If the energy is greater than $E_a$, the collision is effective and leads to product formation.Answer:Therefore, chemical reactions occur when the colliding reactants have energy that is greater than the activation energy.Hence, the correct option is B.