A student heated copper powder in air. The reddish-brown copper turned black. Which statement about this change is correct?
Answer and explanation
Correct answer: Copper has been oxidised to form copper(II) oxide.
On heating in air, copper combines with oxygen: 2Cu + O₂ → 2CuO. Copper changes from elemental copper to copper(II) oxide, and the addition of oxygen is oxidation. The black colour indicates the new oxide, not merely a surface appearance. Thus option B is correct; no copper sulphate or displacement reaction is involved.
Frequently asked questions
What is the correct answer to this question?
Copper has been oxidised to form copper(II) oxide.
Why is this the correct answer?
On heating in air, copper combines with oxygen: 2Cu + O₂ → 2CuO. Copper changes from elemental copper to copper(II) oxide, and the addition of oxygen is oxidation. The black colour indicates the new oxide, not merely a surface appearance. Thus option B is correct; no copper sulphate or displacement reaction is involved.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
