Unit 3

• Reaction rates must be controlled in industrial processes. If the rate is too low then the process will not be economically viable; if it is too high there will be a risk of explosion.
• Collision theory can be used to explain the effects of the following on reaction rates:

   concentration

   pressure

   surface area (particle size)

   temperature

   collision geometry
• A potential energy diagram can be used to show the energy pathway for a reaction.
• The enthalpy change is the energy difference between the products and the reactants.
• The enthalpy change has a negative value for exothermic reactions or a positive value for endothermic reactions.
• The activation energy is the minimum energy required by colliding particles to form an activated complex and can be calculated from potential energy diagrams.
• The activated complex is an unstable arrangement of atoms formed at the maximum of the potential energy barrier, during a reaction.
• A catalyst provides an alternative reaction pathway with a lower activation energy.
• A potential energy diagram can be used to show the effect of a catalyst on activation energy.