2024 H2 Chem P1 Q12 — Transition elements Solution

The answer is A (neither statement is correct).
• Statement 1 is incorrect. Iron is a heterogeneous catalyst: \(\text{N}_2\) and \(\text{H}_2\) are adsorbed onto its surface, forming weak bonds with the iron atoms. These bonds are very much weaker than the covalent bonds within the reacting molecules, so they weaken the bonds within the reactants and the product can still desorb. If the bonds to iron were stronger than those within the reacting molecules, the species would stay stuck on the surface and the catalyst would stop working.
• Statement 2 is incorrect. The ability to form more than one stable oxidation state explains how a transition element acts as a homogeneous catalyst. Iron in the Haber process works by adsorption on its surface, and its oxidation state does not change during the catalysis.
Since both statements are incorrect, the answer is A; B, C and D each accept at least one incorrect statement.