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

Step 1: Understanding the Question:
The question asks to identify the type of catalysis to which the adsorption theory primarily applies.

Step 3: Detailed Explanation:
1. Adsorption Theory of Catalysis: This theory, also known as the contact theory or the intermediate compound formation theory (in specific contexts), describes the mechanism of heterogeneous catalysis. It posits that heterogeneous catalysts function by adsorbing reactant molecules onto their surface.
2. Mechanism of Heterogeneous Catalysis:
* Reactant molecules from the gas or liquid phase are adsorbed onto the surface of the solid catalyst.
* This adsorption activates the reactant molecules, allowing them to react more readily.
* The reaction occurs on the catalyst surface.
* The product molecules then desorb from the catalyst surface, freeing up active sites for new reactant molecules.
3. Types of Catalysis:
* Homogeneous catalysis: Reactants and catalyst are in the same phase. Adsorption is not the primary mechanism here.
* Heterogeneous catalysis: Reactants and catalyst are in different phases (e.g., solid catalyst, gaseous/liquid reactants). Adsorption theory is directly applicable here.
* Auto catalysis: A product of the reaction itself acts as a catalyst.
* Induced catalysis: One reaction makes another reaction possible or faster.
Therefore, adsorption theory is applicable to heterogeneous catalysis.

Step 4: Final Answer:
Adsorption theory is applicable for heterogeneous catalysis.

Answer 2

The question asks which kind of catalysis the adsorption theory is built to explain, so each type of catalysis is checked against what the theory actually describes: reactant molecules sticking to a catalyst's surface.

1. Homogeneous catalysis: Here the catalyst is dissolved in the same phase as the reactants, for example a catalyst and reactants both in solution. Since there is no separate surface for molecules to stick to, surface adsorption is not the operating mechanism.
2. Heterogeneous catalysis: Here the catalyst is in a different phase from the reactants, most often a solid catalyst acting on gaseous or liquid reactants. Reactant molecules land on and stick to the solid surface, get activated, react, and the products then leave the surface - this whole picture is exactly what the adsorption theory describes.
3. Auto catalysis: In this case, one of the products formed during the reaction itself speeds up the same reaction. The explanation for this behaviour centres on the product's own chemical reactivity, not on surface adsorption.
4. Induced catalysis: Here, one reaction occurring in a mixture triggers or accelerates a second, otherwise slow reaction. This is explained through coupling between the two reactions, again with no surface involved.

Only heterogeneous catalysis involves a distinct catalyst surface for reactant molecules to be adsorbed onto, which is the entire basis of the adsorption theory.

Therefore, the correct answer is Heterogeneous catalysis.