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Reduction of Copper Oxide

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A series of free IGCSE Chemistry Activities and Experiments (Cambridge IGCSE Chemistry).

In this activity, copper oxide is reduced by hydrogen to copper.

2CuO + H2 → 2Cu + H2O

Procedure
1. Weigh the reduction tube empty.
2. Place about 3 g of copper(II) oxide along the base of the tube so that it is spread out on the middle of the tube.
3. Reweigh and note the mass of the tube plus copper(II) oxide.
4. Clamp the reduction tube at its open end.
5. Place a safety screen between the tube and the audience. Connect the bung and glass tube to the hydrogen cylinder with rubber tubing, turn on the gas and place the bung in the mouth of the reduction tube.
6. Leave for a further 30 seconds to flush out the air, and light the gas emerging from the hole. Adjust the gas flow to give a flame about 3 cm high.
7. Light the Bunsen burner and with the tip of a roaring flame heat the oxide at one end of the pile. After a few seconds the powder will glow and start to turn pink.
8. Chase this glow along the tube for about 30 seconds until the whole of the black oxide has turned to pink copper. Continue to heat the tube for at least another minute to ensure that all the oxide has reacted.
9. Remove the Bunsen burner and allow the reduction tube to cool with the hydrogen still passing over the copper and the excess gas still burning. This prevents air coming into contact with the hot copper and converting it back to oxide.
10. When the tube is cool enough to handle, turn off the hydrogen at the cylinder, remove the bung and weigh the tube and contents.



Questions
1. Describe the solid copper(II) oxide before heating.
2. Describe the solid remaining after heating.
3. Name the solid formed in the reaction.
4. Write the word and symbol equations for the reactions.
5. What does this reaction tell you about the relative reactivities of hydrogen and copper?
6. Explain why this reaction is a redox reaction.
7. Copper(II) oxide can also be reduced by methane (CH4) although the reaction is slower. The word equation is
Copper(II) oxide + methane → copper + water + carbon dioxide
Write a symbol equation for the reaction.

Answers
  • Show Solutions
    1. Copper(II) oxide is a black, powdery solid.
    2. The solid remaining after heating is a pink solid that conducts electricity.
    3. The solid formed is copper.
    4. copper(II) oxide + hydrogen → copper + water
    CuO + H2 → Cu + H2O
    5. Hydrogen is more reactive than copper because hydrogen displaced copper to form water.
    6. It is a redox reaction because hydrogen is oxidised and copper is reduced.
    7. 4CuO + CH4 → 4Cu + 2H2O + CO2

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