Explain the effect of catalyst on the rate of reaction with diagram.

Explanation

A catalyst is a subtance which alters the rate of reaction without undergoing by change in its amount and chemical composition at the end of the reaction.

According to the concept of activation energy, there is an energy barrier between reactants and products. This is called activation energy barrier. Lower the activation energy barrier, faster is the rate of the reaction. The addition of catalyst provides an alternative path to the reaction by lowering the activation energy. Thus greater number of molecules can cross the energy barrier. Thus fraction of effective colloisions and hence the rate of reaction increases,
Activation energy barrier for a reaction in the presence and absence of catalyst
For a hypothetical reaction :
`A+B rarr AB`
(a) The course of uncatalysed reaction is :
`A+B rarr[A.................B] rarr AB`
Reactants Activated complex Product
(b) The course of catalysed reaction is :

Thus addition of a catalyst to a reaction mixture lowers the activation energy and hence increases the rate of the reactions.