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CAIE IGCSE Chemistry 6.4.9 Redox using oxidation numbers: (a)

CAIE IGCSE Chemistry 6.4.9 Redox using oxidation numbers: (a)
Cambridge IGCSE Chemistry 0620 syllabus for exams in 2026, 2027 and 20282026–2028

Practise assigning oxidation numbers in elements, ions and compounds, then using changes to identify oxidation or reduction.

How this is tested

  • apply rules for uncombined elements, monatomic ions, neutral compounds and ions

Question 17

[Maximum number: 1]

The equation for the reaction between aluminium and copper(II) oxide is shown.

2Al+3CuO→Al2O3+3Cu2 \mathrm{Al}+3 \mathrm{CuO} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+3 \mathrm{Cu}

Which statements about this equation are correct?

1 The oxidation number of the aluminium reactant is +2 .
2 The oxidation number of the aluminium in the product is +6 .
3 The oxidation number of the copper in the reactant is +2 .
4 The oxidation number of the copper product is 0 .

A

1, 2 and 3

B

1 and 2 only

C

3 and 4

D

4 only