Read the passage carefully and answer the questions.

The transition metals and their compounds are known for their catalytic activity. This activity is ascribed to their ability to adopt multiple oxidation states and to form complexes. Vanadium(V) oxide (in Contact Process), finely divided iron, and nickel (in Catalytic Hydrogenation) are some of the examples. Catalysts at a solid surface involve the formation of bonds between reactant molecules and atoms of the surface of the catalyst (first row transition metals utilise 3d and 4s electrons for bonding). This has the effect of increasing the concentration of the reactants at the catalyst surface and also weakening of the bonds in the reacting molecules (the activation energy is lowering). Also because the transition metal ions can change their oxidation states, they become more effective as catalysts.

Which of the following is incorrect about the ability of catalytic action of transition metals?

weakening of the bonds in the reacting molecules-catalyst complex

The correct answer is Option (3) → weakening of the bonds in the reacting molecules-catalyst complex

Core Concept

Catalytic activity of transition metals arises due to:

• Variable oxidation states
• Ability to form complexes
• Surface bonding with reactants

These help lower activation energy.

Explanation

Option 1: Ability to form complexes

Transition metals readily form complexes with reactant molecules. This helps in bringing reactants together and facilitates reaction.

Option 2: Ability to adopt multiple oxidation states

Transition metals can easily change oxidation states. This allows them to participate in redox cycles during catalysis.

Option 3: Weakening of the bonds in the reacting molecules–catalyst complex

Weakening occurs in bonds of reacting molecules when they interact with catalyst surface, not in the catalyst-reactant complex itself as a separate entity. This statement is incorrectly framed.

Option 4: Formation of bonds between reactant molecules and catalyst

Catalysis involves adsorption where bonds are formed between reactants and catalyst surface.