Chemical reactions ordinarily occur as a result of collisions between reacting particles.
In general, the number of collisions per unit time is directly proportional to the concentration of reactants.
In order for collisions to be effective, there must be considerable force in the colllisions. The slower moving molecules do not have enough kinetic energy to react when they collide…they bounce off one another and retain their identity.
Only those molecules moving at high speed have enough energy for collisions to result in a reaction.
Every reaction requires a certain minimum energy for the reaction to occur–it is called activation energy, Ea, and is expressed in kJ.
* it is a positive quantity, Ea>0
* it depends upon the nature of the reaction. “Fast” reactions usually have a small Ea; those with a large Ea usually proceed slowly.
* it is independent of temperature and concentrations.
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