Question

Adsorption theory is applicable for:
A. homogeneous catalysis
B. heterogeneous catalysis
C. autocatalysis
D. induced catalysis

Answer 1

Hint: Adsorption is a phenomenon in which adhesion of molecules and ions takes place on the surface of reactants. This is a type of catalysis reaction which includes adsorption of gases, liquid or solid to the reactant surface.

 Complete step by step answer: The adsorption theory states that adhesion of molecules or ions occur when certain substances are allowed to come close to each other or allowed to contact. Such types of molecular interactions are referred to as surface forces or VanDerWaal forces of attraction. Let us find the applicability of adsorption theory to the given list of catalysis.
Homogeneous catalysis: Homogeneous catalysis is a type of catalysis reaction in which the catalyst is soluble in the reaction medium. This results in a single phase reaction. As there is no other component phase present in the system so no absorption will occur. Palladium catalysed coupling reactions are examples of homogeneous catalysis.
Heterogeneous catalysis: Heterogeneous catalysis is a type of catalysis reaction in which the catalyst is not soluble in the reaction medium. This results in a two phase reaction which consists of solid and liquid. As a result any gas molecule can easily adhere to the surface of the catalyst and can react with the reactant molecules to give products. Hydrogenation is an example of heterogeneous catalysis where hydrogen gas molecules adhere to the surface of the palladium catalyst for addition of hydrogen to reactants.
Autocatalysis: Autocatalysis is a type of catalysis reaction in which one of the reactant molecules acts as a catalyst to carry out the chemical reaction. So there is no need for any absorption of other molecules to begin the reaction. Thus adsorption theory is not applicable to autocatalysis. The glycolysis of sugar molecules to generate ATP is an example of autocatalysis.
Induced catalysis: Induced catalysis is a type of chemical reaction in which one chemical reaction occurs to begin another chemical reaction in a solution mixture. Here no adsorption process is required to bring the chemical transformation. So adsorption theory is not applicable to induced catalysis. The oxidation of sodium arsenite in a mixture of sodium arsenite and sodium sulphite solution occurs by the initial oxidation of sodium sulphite.
Thus the correct option is B; adsorption theory is applicable for heterogeneous catalysis.

Note: The solid catalyst is the most favoured heterogeneous catalyst used for adsorption process. It is easier to recover the catalyst by filtration. Due to such easy handling of the catalyst and low cost they are preferred in industrial synthesis.