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

Step 1: Understanding adsorption theory.
The adsorption theory explains the process where reactant molecules are adsorbed on the surface of a solid catalyst. This theory is primarily applicable in heterogeneous catalysis, where the catalyst is in a different phase from the reactants.
Step 2: Analyzing the options.
(1) Homogeneous catalysis: This involves catalysts and reactants in the same phase and does not follow the adsorption theory.
(2) Heterogeneous catalysis: The adsorption theory is specifically applicable here, as the catalyst is in a different phase (usually solid) and the reactants are adsorbed onto its surface.
(3) Auto catalysis: This is when a product of the reaction catalyzes its own formation. Adsorption theory does not apply in this case.
(4) Induced catalysis: This involves a catalyst being activated by the reactants, not necessarily involving adsorption.
Step 3: Conclusion.
The correct answer is (2) Heterogeneous catalysis.

Answer 2

The adsorption theory of catalysis explains catalytic activity in terms of reactant molecules being adsorbed onto the catalyst's surface, so it only makes sense for a catalyst that exists as a separate phase from the reactants. Let's test each option against that requirement.

1. Homogeneous catalysis: Here the catalyst and reactants exist in the same phase (e.g. both dissolved in solution), so there is no distinct surface for reactants to be adsorbed onto. The adsorption theory does not apply.
2. Heterogeneous catalysis: The catalyst is in a different phase from the reactants - typically a solid catalyst with gaseous or liquid reactants. Reactant molecules physically adsorb onto active sites on the solid surface, weakening their bonds and lowering the activation energy, exactly the mechanism the adsorption theory describes.
3. Auto catalysis: Here one of the reaction's own products speeds up the reaction as it accumulates; the mechanism is about product concentration building up, not about surface adsorption.
4. Induced catalysis: This describes one reaction influencing the rate of another (unrelated) reaction through a common intermediate, which again has nothing to do with surface adsorption.

Only heterogeneous catalysis involves a distinct catalyst surface onto which reactants can adsorb.

Therefore, the correct answer is Heterogeneous catalysis.