NCERT · Class 12 · Chemistry · Chemical KineticsExplain the collision theory of chemical reaction rates. What are the two main criteria for a successful collision leading to product formation?

The collision theory of chemical reactions, proposed by Max Trautz and William Lewis, explains the rate of reactions based on the kinetic theory of gases. According to this theory, reactant molecules are assumed to be hard spheres, and a chemical reaction occurs only when reactant molecules collide with each other with adequate energy and proper orientation. \nFor a collision to be successful and result in product formation, there are two primary criteria:

1. Activation Energy (Energy Barrier): The colliding molecules must possess a minimum amount of kinetic energy during the collision, known as threshold energy or activation energy. Collisions with energy less than this minimum requirement are ineffective and simply bounce off without reacting.
2. Proper Orientation (Steric Factor): Even if molecules possess sufficient energy, collisions will not be successful unless the molecules collide with proper geometric orientation. Proper orientation ensures that the old bonds breaking and new bonds forming occur simultaneously at the correct reactive sites of the molecules.