Magnesium ribbon is placed into dilute hydrochloric acid. Bubbles of gas are produced and the magnesium disappears. Explain what has happened to the magnesium atoms and to the hydrogen ions in terms of oxidation and reduction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Magnesium ribbon reacts vigorously with dilute hydrochloric acid. The solid magnesium disappears and bubbles of a colourless gas are produced.
Model answer (4 marks)
Magnesium atoms lose electrons and are oxidised.
Hydrogen ions gain electrons and are reduced.
Hydrogen ions gain electrons and are reduced.
Examiner tips
- Use the word ‘oxidised’ for magnesium and ‘reduced’ for hydrogen. Show the electron transfer: Mg → Mg²⁺ + 2e⁻ and 2H⁺ + 2e⁻ → H₂.
- common_mistakes
- :
- Confusing ‘oxidised’ with ‘reduced’ for magnesium. Forgetting to mention that hydrogen ions are reduced to hydrogen gas.
Mark scheme (4 marks)
- Magnesium atoms lose electrons
- Magnesium is oxidised
- Hydrogen ions gain electrons
- Hydrogen ions are reduced
Key terms in this question
oxidation · reduction · hydrogen ions
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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