In heterogeneous catalysis, what is the correct sequence of steps for the catalyst’s mode of action?

In heterogeneous catalysis, what is the correct sequence of steps for the catalyst’s mode of action?

• A. Adsorption, Activation / bond weakening, Reaction, Desorption
• B. Desorption, Adsorption, Activation, Reaction
• C. Activation, Adsorption, Desorption, Reaction
• D. Adsorption, Desorption, Activation, Reaction

Answer: (A)

In a heterogeneous catalyst, the surface provides sites where reactant molecules can attach and interact closely. First, adsorption captures the reactants on the surface, increasing their local concentration and orienting them for reaction. Next, the adsorbed species are activated—their bonds are weakened by interaction with the surface, lowering the energy barrier for transformation. Then the chemical change occurs while the species remain on the surface, forming products that are still bound to the catalyst. Finally, these products desorb from the surface, freeing active sites for another catalytic cycle. This sequence—adsorption, activation, reaction, desorption—best explains how the catalyst facilitates the process.

In a heterogeneous catalyst, the surface provides sites where reactant molecules can attach and interact closely. First, adsorption captures the reactants on the surface, increasing their local concentration and orienting them for reaction. Next, the adsorbed species are activated—their bonds are weakened by interaction with the surface, lowering the energy barrier for transformation. Then the chemical change occurs while the species remain on the surface, forming products that are still bound to the catalyst. Finally, these products desorb from the surface, freeing active sites for another catalytic cycle. This sequence—adsorption, activation, reaction, desorption—best explains how the catalyst facilitates the process.