Question

For which of the following is the adsorption theory applicable?

• A. Homogeneous catalysis
• B. Heterogeneous catalysis
• C. Auto catalysis
• D. Induced catalysis

Hint:

Adsorption theory is particularly important in heterogeneous catalysis, where the catalyst adsorbs the reactants on its surface.

Answer 1

The Correct Option is B

Adsorption theory explains catalysis through reactants binding to active sites on a catalyst's surface.
This requires the catalyst to be in a separate phase from the reactants, which rules out homogeneous catalysis (same phase), auto catalysis (product-driven), and induced catalysis (intermediate-driven).
Only heterogeneous catalysis involves a solid catalyst surface adsorbing gas or liquid-phase reactant molecules, which is exactly what the adsorption theory models.
So the correct answer is Heterogeneous catalysis.

Answer 2

Think about what "adsorption" actually requires physically: molecules sticking to a surface. Let's check which type of catalysis has such a surface available.

1. Homogeneous catalysis: Catalyst and reactants are uniformly mixed in one phase (e.g. an acid catalyst dissolved in the same liquid as the reactants), so there's no interface for adsorption to occur on.
2. Heterogeneous catalysis: A solid catalyst (like platinum or nickel) provides a distinct surface with active sites; gas or liquid reactant molecules adsorb onto these sites, react, and the products then desorb. This is precisely the physical picture the adsorption theory is built on.
3. Auto catalysis: The reaction is sped up by its own product mixing into the same phase as the reactants - again, no separate solid surface is involved.
4. Induced catalysis: One reaction promotes a second reaction via a shared intermediate, without any surface adsorption step.

Since a physical adsorbing surface only exists when the catalyst is in a different phase from the reactants, the adsorption theory applies specifically to heterogeneous catalysis.

Therefore, the correct answer is Heterogeneous catalysis.