A2 Kinetics

A2 Kinetics

1. Rate of Reaction: the change in concentration of reactants and products in a reaction per unit time

   • Units of Rate: moldm-3s-1

2. Order of Reaction: the power to which a species is raised to in the rate equation

   • 1st Order
     • Rate is directly proportional to concentration of species
   • 2nd Order
     • Rate is directly proportional to square of species concentration
   • 0 Order
     • Species has no effect on rate
   • Overall order: all the orders in rate equation added together

3. Reactions often have multiple 'steps' as there are many ions/molecules so they are unlikely to all collide at once

   • Mechanism: separate steps leading from reactants to products

4. Rate Determining Step (RDS): the slowest step in the mechanism

   • Reaction is only as fast as its slowest step so the RDS determines overall rate

5. Determine K by:

   • Rate / [A][B]

6. A temperature increase leads to an increase in K

7. For a 1st order overall reaction the unit of k is s -1

   • For a 2nd order overall reaction the unit of k is mol-1dm3s -1
     • For a 3rd order overall reaction the unit of k is mol-2dm6s -1