Question

In auto-catalysis, one of the ______ of the reaction acts as a catalyst.
(a) intermediates
(b) products
(c) reactants
(d) none of the above.

Answer 1

Hint: Catalyst is a substance which when added to a reaction, increases the rate of the reaction. In some reactions without an addition of a substance, the rate can be increased.

Complete step by step answer:
Catalysts are generally foreign substances, but sometimes one of the products formed in a reaction can act as a catalyst. That is, it can increase the rate of the reaction. Such a catalyst is called an auto catalyst. This phenomenon is called auto catalysis.
An example for autocatalysis is when oxalic acid is titrated with potassium permanganate in the presence of dilute sulphuric acid. The colour of potassium permanganate first slowly fades and then it fades faster due to the formation of manganese ions which have the ability to act as auto catalysts.
\[2KMn{{O}_{4}}+3{{H}_{2}}S{{O}_{4}}+5{{H}_{2}}{{C}_{2}}{{O}_{4}}\to {{K}_{2}}S{{O}_{4}}+2MnS{{O}_{4}}+8{{H}_{2}}O+10C{{O}_{2}}\]

Thus, in auto-catalysis one of the products of the reaction acts as a catalyst. The correct answer is the option (b).

Additional Information:
Auto catalytic reactions are generally very slow at the starting of the reaction. But as the reaction continues, its rate increases. A set of chemical reactions can be said to be collectively autocatalytic if a number of those reactions produce, as reaction products, which have the ability to catalyse for enough of the other reactions that the entire set of chemical reactions is self-sustaining at a given amount of energy and food molecules. A chemical reaction can undergo autocatalysis, if only the reaction product is itself the catalyst for that reaction. That is why there is no reactant catalysis and solvent catalysis.

Note: It is often mistaken that the intermediate formed, can act as an auto catalyst. But this is not the case. The products are the ones which act as auto catalysts.