Characteristics of catalysis
The following are the characteristics which are common to must of catalytic reactions.
(1) A catalyst remains unchanged in mass and chemical composition at the end of the reaction.
(2) A small quantity of the catalyst is generally sufficient to catalyses almost unlimited reactions
(i) For example, in the decomposition of hydrogen peroxide, one gram of colloidal platinum can catalyses litres of hydrogen peroxide.
(ii) In Friedel craft’s reaction, anhydrous aluminium chloride is required in relatively large amount to the extent of 30% of the mass of benzene,
(3) The catalyst can not initiate the reaction: The function of the catalyst is to alter the speed of the reaction rather than to start it.
(4) The catalyst is generally specific in nature: A substance, which acts as a catalyst for a particular reaction , fails to catalyse the other reaction , different catalysts for the same reactant may for different products.
(5) The catalyst can not change the position of equilibrium : The catalyst catalyse both forward and backward reactions to the same extent in a reversible reaction and thus have no effect on the equilibrium constant.