Topic 6: Chemical Kinetics

6.1 Collision Theory and Rates of Reaction

Rate of reaction

  • Definition: the change in concentration of products or reactions per unit of time

  • Measured through:

    • pH

    • Electric conductivity

    • Change in mass or volume

    • Change in colour

  • Average rate

  • Instantaneous rate​

​​Activation energy

  • Definition: the minimum amount of energy required for molecules with favourable collisions leading to the formation of the activated complex and later the products



  • Definition: compounds or substances that increase the rate of a reaction by decreasing the activation energy.

  • Homogeneous catalyst: same phase as reactants

    • Example: chlorine in the depletion of ozone

  • Heterogeneous catalyst: different phase as reactants

    • Example: platinum and palladium in car catalytic converters

Maxwell-Boltsmann energy distribution curve