Transition metals are used as catalysts in many important industrial processes. Explain why transition metals are able to act as catalysts, and give two examples of transition metals used as catalysts in named industrial processes.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Transition metals can adopt several oxidation states, giving them variable valency.
This allows them to accept and donate electrons during a reaction, facilitating electron transfer and lowering the activation energy.
Example 1: Iron (Fe) is used as a catalyst in the Haber process for the synthesis of ammonia.
Example 2: Nickel (Ni) is used as a catalyst in the hydrogenation of vegetable oils to produce margarine.
This allows them to accept and donate electrons during a reaction, facilitating electron transfer and lowering the activation energy.
Example 1: Iron (Fe) is used as a catalyst in the Haber process for the synthesis of ammonia.
Example 2: Nickel (Ni) is used as a catalyst in the hydrogenation of vegetable oils to produce margarine.
Examiner tips
- Use the term ‘variable valency’ or ‘variable oxidation states’ to gain the first point. Show that this property enables electron transfer to lower activation energy. Give two distinct catalysts and match each to a specific industrial process.
- common_mistakes
- :
- Writing non‑transition metals (e.g. sodium) as catalysts. Failing to match the catalyst to the correct process. Not mentioning the variable oxidation state or electron transfer mechanism.
Mark scheme (5 marks)
- Transition metals can have variable oxidation states (variable valency)
- This allows them to accept and donate electrons during a reaction (facilitating electron transfer)
- Named transition metal catalyst correctly identified (e.g. iron, nickel, platinum, vanadium(V) oxide / vanadium pentoxide)
- Correct industrial process matched to first named catalyst (e.g. iron — Haber process / manufacture of ammonia; nickel — hydrogenation of vegetable oils / margarine production; platinum — catalytic converters / Ostwald process; vanadium(V) oxide — Contact process / manufacture of sulfuric acid)
- A second, different named transition metal catalyst correctly matched to a different named industrial process
Key terms in this question
Related
- All AQA A-Level Chemistry (7405) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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