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

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RRB Technician Grade III Official Paper (Held On: 29 Dec, 2024 Shift 3)
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  1. Black-coloured copper (I) oxide 
  2. Brown-coloured copper(II) oxide 
  3. Black-coloured copper (II) oxide  
  4. Blue-coloured copper(II) oxide 

Answer (Detailed Solution Below)

Option 3 : Black-coloured copper (II) oxide  
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Detailed Solution

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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.

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