Extracting metals with charcoal
40
In each of the two experiments, illustrating the idea of competition between metals and
carbon, students heat a metal oxide with powdered charcoal. If the carbon is more reactive
than the metal it will remove the oxygen from the metal oxide and leave traces of the
metal in the reaction vessel. The first experiment uses lead(II) oxide; the second modifies the
technique slightly and uses copper(II) oxide.
Lesson organisation
The solids may be dispensed in plastic weighing dishes. It is best not to issue all three solids
at the same time because students may confuse the charcoal and the copper oxide.
The experiment should take about 30 minutes.
Apparatus and chemicals
Eye protection
Each student or pair of students will require:
•
Small, hard glass test-tubes (ignition) tubes, 3 (see note 1)
Test-tube holder
Test-tube rack
Spatula
Plastic weighing dish (boat)
Heat resistant mat
Access to:
Lead(II) oxide (Toxic, Dangerous for the environment), about 1 g (see note 2)
Powdered charcoal, about 2 g
Copper(II) oxide (Harmful, Dangerous for the environment), about 1 g
Technical notes
Lead(II) oxide (Toxic, Dangerous for the environment) Refer to CLEAPSS® Hazcard 56
Copper(II) oxide (Harmful, Dangerous for the environment) Refer to CLEAPSS® Hazcard 26
1 Test-tubes made of heat resistant borosilicate glass (Pyrex or similar) must be used. Testtubes with a capacity of about 10 cm3 are ideal. It is important that the test-tubes are dry.
Heating lead and its compounds strongly in glass often results in the lead compounds
fusing into the glass, rendering the test-tube impossible to re-use. If this is an issue, old
but unstained test-tubes can be used and discarded after this use.
2 The three solids may be dispensed in separate, labelled, plastic weighing dishes. It is wise
to withhold the copper(II) oxide until it is required to avoid the students confusing it with
the charcoal.
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Procedure
HEALTH & SAFETY: Wear eye protection throughout. The room should be well ventilated.
Experiment 1
a Transfer one small spatula measure of lead(II) oxide to the empty weighing dish.
b Add one spatula measure of charcoal powder.
c Mix the two powders together using a spatula.
d Transfer the mixture into a hard-glass test tube and strongly heat this mixture for five
minutes in a Bunsen flame.
e Allow the test-tube to cool in its holder on a heat resistant mat.
f Tip the cooled mixture out onto the heat
resistant mat.
ignition tube
Experiment 2
a Transfer one spatula measure of copper(II)
oxide to a hard glass test-tube.
b Carefully add one spatula of charcoal
powder on top of the copper oxide
without any mixing.
c Strongly heat these two layers for five
minutes in a Bunsen flame.
charcoal
copper oxide
Bunsen burner
d Allow to cool and then look closely at
where the powders meet in the test-tube.
heat resistant mat
Teaching notes
In each case the students should look for signs that reaction has occurred producing the
metal. The copper should be obvious from its colour. The lead may be less obvious; it may
appear as globules or as grey powder.
The reactions confirm the place of carbon in the reactivity series, above lead and copper, as
it reduces the metal oxides to the metals and is itself oxidised to carbon dioxide:
2CuO(s) + C(s) → 2Cu(s) + CO2(g) and 2PbO(s) + C(s) → 2Pb(s) + CO2(g)
Reference
This experiment has been reproduced from Practical Chemistry:
http://www.practicalchemistry.org/experiments/intermediate/metals/extracting-metals-withcharcoal,305,EX.html
Useful resource
Several other experiments in this book also illustrate the competition principle. Examples include:
Experiment 39: Displacement reactions between metals and their salts
Experiment 42: The reaction between zinc and copper oxide
Experiment 43: The thermite reaction
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Updated 22 Apr 2009