Activation energy: there are two theories about the activation
energy:1.collision theory: according to the collision theory ,the reaction occurs
when the reactants molecules A and B come very close to each other or
collide. Only those collisions result in product formation in which the
colliding molecules are associated with a certain minimum amount of
energy . this minimum energy which the molecule should possess so that
their mutual collision result in a chemical reaction is called "threshold
energy". Collisions among molecules possessing energy less than
threshold energy are not effective collisions and do not result in the
formation of products. The additional energy required by the molecule
to attain the threshold energy is called activation energy.
2.transition state theory: the molecules must be in an activated state
before they can react. There is a minimum energy level denoted by Ex to
whuch the reactant molecule must be raised to enable it to undergo a
chemical change. The activation energy is the energy required to form
the activated complex or intermidate.
Effect of temperature on rate of reaction:there is a significient
relationship between the rate of chemical reaction and the temperature
at which the reaction takes place. For homogeneous reactions ,it is
usually found that the velocity constant of the reaction is approximately
doubled for every ten degree rise in temperature and the realationship
can be represented by
Which is Arrhenius equation.