Which process is the first step in the mode of action of a heterogeneous catalyst?

Which process is the first step in the mode of action of a heterogeneous catalyst?

• A. Adsorption
• B. Activation
• C. Reaction
• D. Desorption

Answer: (A)

In heterogeneous catalysis, the process starts with adsorption of the reactant molecules onto the solid catalyst surface. This attachment concentrates the reactants at the active sites and orients them in a way that makes it easier for bonds to break and new bonds to form. Once adsorbed, the molecules are activated—often through interactions with the metal surface that weaken certain bonds and create reactive intermediates. The actual chemical transformation then occurs on the surface, and finally the products desorb, leaving the surface free to bind more reactants. If desorption or the surface reaction happened first, there would be nothing on the surface to drive the required bond changes. So the first step is adsorption.

In heterogeneous catalysis, the process starts with adsorption of the reactant molecules onto the solid catalyst surface. This attachment concentrates the reactants at the active sites and orients them in a way that makes it easier for bonds to break and new bonds to form. Once adsorbed, the molecules are activated—often through interactions with the metal surface that weaken certain bonds and create reactive intermediates. The actual chemical transformation then occurs on the surface, and finally the products desorb, leaving the surface free to bind more reactants. If desorption or the surface reaction happened first, there would be nothing on the surface to drive the required bond changes. So the first step is adsorption.