Explain why transition elements are widely used as catalysts in industrial chemical processes.

Cambridge International IGCSE Chemistry (0620) — 8.4 Transition elements · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Many important industrial reactions, such as the manufacture of ammonia and the production of sulfuric acid, rely on catalysts made from transition elements.

Model answer (4 marks)

1. Transition elements can exhibit a range of oxidation states.
2. This variable valency allows them to accept and donate electrons, forming temporary bonds with reactants.
3. By providing an alternative reaction pathway, the catalyst lowers the activation energy.
4. The catalyst is not consumed and remains unchanged after the reaction.

Examiner tips

Use the exact terms: variable oxidation states, accept/donate electrons, lower activation energy, unchanged catalyst.
Show the logical sequence: valency → electron transfer → lower E‡ → catalyst unchanged.
Keep each point concise and separate with numbers or bullets.

Common mistakes

Confusing ‘variable valency’ with ‘variable oxidation states’ or vice versa.
Failing to mention that the catalyst is not used up.
Omitting the point about lowering activation energy or the role of temporary bonds.

Mark scheme (4 marks)

Transition elements can have variable oxidation states (variable valency)
This allows them to accept and donate electrons during a reaction (or: to form temporary bonds with reactants)
The catalyst lowers the activation energy of the reaction
The catalyst is not used up / remains chemically unchanged at the end of the reaction

Key terms in this question

transition elements · catalyst