Answer : If you add catalyst to a reaction mixture it would increase its rate of reaction to certain extent after sometime the reactant molecules will start regenerating the catalyst molecule again. There will be one moment where reactant molecule will not require any more catalyst and on their own they will do the reaction. The main function of catalyst is to lower the activation energy of the reaction irrespective of decomposition or generation of any product.
A catalyst is a substance which increases the rate of a reaction by taking the reaction through a different path which involves lower activation energy and thus more molecules can cross the energy barrier and convert to products.
Activation energy is the extra energy that must be supplied to reactants in order to cross the energy barrier and thus convert to products.
The catalyst itself does not take part in the chemical reaction and is regenerated as such at the end.
Thus the rate for the decomposition of hydrogen peroxide increases on addition of catalyst by lowering the activation energy.
