February 13, 2014
Energy Changes and Activation Energy
Chemical reactions take place when particles collide
A successful collision must have
- a minimum amount of kinetic energy
- the correct geometry (the particles must align correctly)
Activation energy (Ea)
is the minimum collision energy required for a reaction
February 13, 2014
Ep diagrams can include Ea
February 13, 2014
What is ∆H, Ea for this reaction?
The transition state (or activated complex) is an unstable
compound between the products and reactants (higest Ep)
February 13, 2014
Lowering Ea for a reaction will speed it up
A catalyst is a substance that increases the rate of a
reaction without being consumed by the reaction
It provides an alternate pathway for the reaction to
take place
This alternate pathway has a lower Ea
The catalyst has no effect on ∆H
February 13, 2014
Catalysts are used in industrial processes
Enzymes are biological catalysts
Enzymes allow chemical reactions to take place at body
temperature by lowering Ea
They are large protein molecules
February 13, 2014