Question

For which of the following is the adsorption theory applicable?

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

Hint:

Remember the key distinguishing factor in catalysis: the phase of the catalyst relative to the reactants. Heterogeneous (different phases) catalysis is often surface-mediated and involves adsorption.

Answer 1

The Correct Option is B

Another way to reach the same answer is to lay out the actual steps the adsorption theory proposes, and see which type of catalysis needs every one of those steps to make sense.

1. Diffusion: Reactant molecules must first travel from the bulk phase toward the catalyst's surface - this step only makes sense if the catalyst is a separate phase from the reactants in the first place.
2. Adsorption: The reactant molecules attach to active sites on that surface, weakening their internal bonds and making them more reactive.
3. Reaction: With bonds already weakened, the reaction takes place directly on the surface, needing far less energy than it would in free space.
4. Desorption: The newly formed product molecules detach from the surface, freeing up the active sites for fresh reactant molecules.

Every one of these four stages assumes a solid surface that is physically distinct from the reactants, which is precisely the setup found in heterogeneous catalysis - homogeneous, auto, and induced catalysis do not involve this kind of surface at all, so none of the adsorption steps would apply to them.

The correct answer is Heterogeneous catalysis.