Which of the following is produced when copper is heated in the presence of air? 

The correct answer is Black-coloured copper (II) oxide.

Key Points

• When copper is heated in the presence of air, it reacts with oxygen to form copper (II) oxide (CuO).
• Copper (II) oxide is a black-coloured compound.
• The reaction can be represented as: 2Cu + O₂ → 2CuO.
• This process is a type of oxidation reaction, where copper gains oxygen to form copper (II) oxide.
• Heating copper in the presence of air ensures that there is an adequate supply of oxygen for the reaction to take place.

 Additional Information

• Black-coloured copper (I) oxide
  • Copper (I) oxide (Cu₂O) is actually red or reddish-brown in colour, not black.
  • It is formed by the reduction of copper (II) compounds.
• Brown-coloured copper(II) oxide
  • Copper (II) oxide is not brown; it is black in colour.
  • Brown colour might be confused with copper metal itself which has a reddish-brown hue.
• Blue-coloured copper(II) oxide
  • Copper (II) oxide is not blue; it is black in colour.
  • Blue colour is typically associated with copper (II) sulfate (CuSO₄), a different compound.