Titanium is a metal used to make replacement hip joints and jet engine parts. It is extracted from titanium(IV) oxide by first converting the oxide to titanium(IV) chloride, then reacting the chloride with sodium or magnesium. Explain why titanium cannot be extracted from titanium(IV) oxide by heating with carbon, and why sodium or magnesium can be used instead.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Titanium(IV) oxide cannot be reduced by carbon because titanium is more reactive than carbon. Industrial extraction uses sodium or magnesium to displace titanium from titanium(IV) chloride.
Model answer (4 marks)
Carbon can only reduce metals that are less reactive than it. Titanium is more reactive than carbon, so carbon cannot displace titanium from its oxide.
Sodium (or magnesium) is more reactive than titanium. Therefore it can displace titanium from its chloride (or oxide) and reduce it to the metal.
Sodium (or magnesium) is more reactive than titanium. Therefore it can displace titanium from its chloride (or oxide) and reduce it to the metal.
Examiner tips
- State the reactivity relationship first, then explain the consequence.
- Use the exact phrase ‘more reactive than’ to match the mark scheme.
- Show the two steps: (1) carbon fails because titanium is more reactive, (2) sodium/magnesium succeeds because they are more reactive than titanium.
Common mistakes
- Claiming carbon can reduce titanium without citing reactivity order.
- Confusing ‘displace’ with ‘reduce’ and not linking to the reactivity series.
- Using the wrong order of reactivity (e.g., saying sodium is less reactive than titanium).
Mark scheme (4 marks)
- Carbon can only reduce (displace) metals that are less reactive than carbon
- Titanium is more reactive than carbon, so carbon cannot displace/reduce titanium from its oxide
- Sodium (or magnesium) is more reactive than titanium
- Sodium or magnesium can therefore displace/reduce titanium from its compound
Related
- All WJEC GCSE Chemistry (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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