CHEM102 Lecture Notes - Lecture 4: Threshold Energy, Collision Theory, Kinetic Energy

• School: University of Alberta
• Department: Chemistry
• Course: CHEM102
• Professor: Camille De Browne- Forbes

Document Summary

Particles must collide (and with sufficient energy) to react. If concentration increases, number of particles increases so rate of reaction increases. We already know that concentrations are multiplied in the rate law and not added. This is because the number of collisions depend on the product of the number of reactant particles, not the sum. The nuclei attract and overlap: the threshold energy is also called activation energy, ea, ea is always positive. Molecules need to collide to react but that is not enough. They should also have : proper orientation, threshold energy. This is an exothermic reaction because more energy is given off while forming bonds than used up while breaking bonds. Importance of molecular orientation to an effective collision. Z = collision frequency = number of collisions per unit time per volume. F = fraction of molecules with energy greater than or equal to the activation energy f = e-ea/rt k = p z e-ea/rt.