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Extracting Metals with Carbon

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

In this activity, copper and lead are extracted from their oxides using powdered charcoal.

2CuO + C → 2Cu + CO2
2PbO + C → 2Pb + CO2

Procedure
1. Transfer one spatula measure of copper(II) oxide to a hard-glass test-tube.
2. Carefully add one spatula of charcoal powder on top of the copper(II) oxide without any mixing.
3. Strongly heat these two layers for 5 minutes in a Bunsen flame.
4. Allow the tube to cool and then look closely at where the two powders meet in the test tube

Reduction of Copper Oxide
Black copper oxide and black carbon powder are mixed together and heated up.
The gas evolved is passed into a solution of calcium hydroxide (lime water), a white precipitate of calcium carbonate is formed as the gas passes through the lime water. This shows that carbon dioxide is being produced.
As the mixture is heated, the copper oxide is reduced to red copper by the carbon. After the mixture is cooled, you can see it is red-brown due to the copper produced by the reduction.



Questions
1. Describe the solid copper(II) oxide before heating.
2. Name the gas formed in the reaction.
3. Describe the solid remaining after heating.
4. Name the solid formed in the reaction.
5. Write the word and symbol equations for the reactions.
6. What does this reaction tell you about the relative reactivities of carbon and copper?
7. Explain why this reaction is a redox reaction.

Answers
  • Show Solutions
    1. Copper(II) oxide is a black, powdery solid.
    2. The gas formed is carbon dioxide.
    3. The solid remaining after heating is a pink solid.
    4. The solid formed is copper.
    5. copper(II) oxide + carbon → copper + carbon dioxide
    2CuO + C → 2Cu + CO2
    6. Carbon is more reactive than copper because carbon displaced copper to form carbon dioxide.
    7. It is a redox reaction because carbon is oxidised and copper is reduced.
Reduction of Lead Oxide, Copper Oxide, Iron Oxide
1. Transfer one small spatula measure of lead(II) oxide to the empty weighing dish.
2. Add one spatula measure of powdered charcoal.
3. Mix the two powders together using the spatula.
4. Transfer the mixture into a hard-glass test tube and strongly heat this mixture for 5 minutes in a Bunsen flame.
5. Allow the test tube to cool in its holder on a heatproof mat.
6. Empty the cooled mixture out on to the heatproof mat.
7. Repeat the above with copper oxide and iron oxide Questions
1. Why is the iron oxide unchanged when it is heated with carbon?

Answers
  • Show Solutions
    1. The temperature needs to be much higher than that achieved by a bunsen burner, and the reduction of iron oxide is usually achieved using gaseous carbon monoxide rather than solid carbon.


Describe in outline, the extraction of zinc from zinc blende
2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g)
ZnO(s) + C(s) → Zn(l) + CO(g)

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