If carbon removes oxygen from a metal oxide under the conditions given, the oxide has been reduced. In the school reactivity model, this supports placing the metal below carbon. A failed reduction can support the opposite conclusion in a controlled comparison.
The 2027 SEC G3 Chemistry K324 syllabus relates the reactivity series to whether metal oxides can be reduced by carbon or hydrogen. This guide shows how to infer a relative order from the observations supplied.
- Look for evidence that the metal formed.
- Describe reduction as loss of oxygen in this example.
- Compare oxides tested under similar conditions.
- Use only the relationships the evidence supports.
CHAPTER 1 OF 4 · Back to contents
Keep the observation separate from the interpretation
Reduction in this context means oxygen is removed from the metal oxide. When a question identifies the solid product as the metal, you can infer that reduction occurred.
The carbon takes up oxygen. If the question specifies carbon dioxide as the product, one balanced equation for copper(II) oxide is 2CuO + C → 2Cu + CO₂.
A colour change alone should be described as an observation. Use the information supplied about product identity to explain the reaction.
CHAPTER 2 OF 4 · Back to contents
Worked example | Compare copper and magnesium oxides
In an exam comparison, copper(II) oxide and magnesium oxide are each heated with carbon under the stated conditions. The question reports the following results.
| Starting oxide | Reported result | School-model inference |
|---|---|---|
| Copper(II) oxide | Copper is formed | Copper is below carbon |
| Magnesium oxide | No magnesium is formed | Consistent with magnesium above carbon |
The results support the order magnesium, carbon, copper from higher to lower reactivity in this model. Magnesium oxide is more difficult for carbon to reduce under the given conditions.
For the copper equation, copper oxide loses oxygen and is reduced. Carbon gains oxygen and is oxidised.
Contents · Previous chapter · Next chapter
CHAPTER 3 OF 4 · Back to contents
Practise deciding what the test can rank
Suppose two different oxides both give their metals when heated with carbon. That observation places both metals below carbon in the school model.
It does not tell you which of the two metals is more reactive. To rank them, use another comparison such as displacement evidence supplied in the question.
If heating time or temperature differed between two tests, check that difference before attributing a failed result solely to reactivity.
Contents · Previous chapter · Next chapter
CHAPTER 4 OF 4 · Back to contents
Frequently asked questions
Does carbon have to be a metal to be used as a reference?
Carbon is a non-metal. It is useful as a reference for whether certain metal oxides can be reduced by it.
Which substance is the reducing agent in the copper example?
Carbon is the reducing agent because it removes oxygen from copper(II) oxide.
Should I propose trying the reaction outside class?
Treat this as an exam interpretation. Any practical work follows the teacher’s laboratory instructions.
Contents · Previous chapter · Continue with the related guide