Characters of a catalyst
The concentration of the catalyst should be very small when compared to the concentration of the reactant
The catalyst can be regenerated at the end of a reaction
Position of the equilibrium is not disturbed by the presence of catalyst in an equilibrium reaction. The impact of the catalyst is same on both the forward and reverse reactions
It should be noted that the catalyst never initiate any reaction
Catalyst has no influence on the nature of the products formed
There are some substances which retard the rate of the reaction by poisoning the catalyst.This substance is called catalytic poison. For example in the contact process of preparation of sulphur trioxide by the combination of sulphur dioxide and oxygen , arsenic acts as a catalytic poison even present in trace amount.