Explain why transition metals are often used as catalysts in industrial processes. Give two properties of transition metals that make them suitable for this role, and for each property give one example.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Transition metals and their compounds are widely used as catalysts in the chemical industry.
Model answer (4 marks)
Transition metals are useful as catalysts because they can adopt several oxidation states, allowing them to accept and donate electrons during a reaction.
1. Variable oxidation states – e.g. iron in the Haber process can cycle between Fe²⁺ and Fe³⁺, facilitating the reduction of N₂ to NH₃.
2. High melting point and hardness – e.g. nickel used in hydrogenation of vegetable oils is robust at the high temperatures required, so the catalyst remains intact.
These properties enable transition metals to act as efficient, durable catalysts in industrial chemistry.
1. Variable oxidation states – e.g. iron in the Haber process can cycle between Fe²⁺ and Fe³⁺, facilitating the reduction of N₂ to NH₃.
2. High melting point and hardness – e.g. nickel used in hydrogenation of vegetable oils is robust at the high temperatures required, so the catalyst remains intact.
These properties enable transition metals to act as efficient, durable catalysts in industrial chemistry.
Examiner tips
- Use the word ‘variable oxidation states’ to show understanding of electron transfer; give a specific metal example. Mention the high melting point/strength and link it to industrial conditions. Keep the answer concise and directly tied to the marks scheme.
Common mistakes
- Confusing ‘variable oxidation states’ with ‘multiple elements’ – the key is the metal’s ability to change charge. Giving a non‑transition metal example (e.g. copper) or a non‑catalytic property. Omitting the example or using a vague statement such as ‘high temperature’ without naming the metal.
Mark scheme (4 marks)
- Transition metals can form ions with different charges / oxidation states (variable oxidation states)
- This allows them to transfer electrons / accept and donate electrons during reactions (enabling catalytic activity)
- Correct named example of a transition metal used as a catalyst, e.g. iron in the Haber process / nickel in the hydrogenation of vegetable oils / vanadium(V) oxide in the Contact process
- Transition metals have high melting points / are hard and strong, making them durable under the harsh conditions (high temperatures / pressures) of industrial processes
Key terms in this question
Related
- All AQA GCSE Chemistry (8462) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →