formula of copper oxide using methane reduction

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					IGCSE chemistry
The reduction of copper oxide to copper – finding the formula of copper oxide

Methane can be used to turn copper oxide into
copper.
Methane is passed over a heated sample of
copper oxide in a tube. Most of the methane does
not react – it is burnt off at the exit of the tube.
During the experiment, you can see a colour
change as black copper oxide becomes copper.
Once the black copper oxide has all turned into
copper, heating can stop, but the methane is still
passed over the hot copper until it cools down.




Questions

1. What type of reaction is taking place when copper oxide turns into copper?
2. What happens to the methane which reacts?
3. How do you know when the reaction is over?
4. Why is methane passed over the hot copper whilst it cools down?
5. Give two specific safety precautions when carrying out this experiment.

Calculations

A student collected the following data:

                                                                        mass (g)
mass of empty tube                                                      23.52
mass of tube with black copper                                          25.55
mass of tube, after heating, with copper                                25.14

Calculate the following:

1. the mass of black copper oxide used in the experiment
2. the mass of copper left at the end of the experiment
3. the mass of oxygen contained in the copper oxide
4. the ratio of copper atoms (Ar = 63.5) to oxygen atoms (Ar = 16) in the black copper oxide
5. the formula of the copper oxide.

(the diagram is from http://www.practicalchemistry.org/experiments/finding-the-formula-of-copper-oxide,210,EX.html)

				
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posted:12/20/2011
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