Controlling the Rate

Controlling the Rate

1. Collision Theory

   • Reactant molecules must collide with enough energy for chemical reaction to occur
   • Activation energy (Ea) - minimum kinetic energy required for reaction to occur
   • Activated Complex - Intermediate stage, high energy, unstable arrangement of atoms
   • Energy given out when new bonds form as atoms rearranged into product molecules

2. Reaction Rates

   • average rate = change in quantity/change in time
   • relative rate = 1/t

3. Altering Factors

   • Temperature
     • Temp increase, then particles have more kinetic energy and so an increased chance of possible collisions
   • concentration
     • Conc increase, then more particles, so more collisions so increase in rate of reaction
   • Particle size
     • Particle size decrease, then larger surface area, increased chance of collisions, faster rate
   • Use of Catalyst
     • Lowers Activation Energy, provides alternative route, provides surface for reaction to occur on
     • Homogenous - same state Heterogenous - different state