Reduction of copper with methane gas.
Prepare a class set of test tubes for the reduction of copper oxide. Stopper the test tube and heat strongly near the end of the tube as shown on the right. As the gas heats inside the tube it expands and eventually punches a hole through the tube.
Step 1 Weigh the empty test tube prepared earlier.
Step 2 Place a small amount, approximately 1.00 gram, of copper oxide in the test tube and spread it out to maximise surface area. Reweigh the test tube with the copper oxide.

 

 

Step 3 Assemble the apparatus as shown on the right. Ensure the test tube is clamped near the neck away from the copper oxide and the hole in the test tube is pointing upwards.

Step 4 Connect the test tube to the gas and allow the gas to pass through for no more than 30 seconds. This will ensure that all oxygen is removed from the tube.

Step 5. Keeping your head well away from the test tube, ignite the gas coming from the test tube, as shown on the right. Turn the gas down so the flame is only about 7 cm high.

 
Step 6. Using a Bunsen gently heat the copper oxide at first, then heat strongly for about 5 minutes moving the Bunsen back and forth under the sample until it changes to a brown colour.

Step 7 When the copper sample has changed to a brown colour remove the Bunsen but continue to pass gas through the test tube and burning it at the end for 10 minutes until the test tube returns to room temperature. This will stop reoxidation of copper back to copper oxide.

 

  
Step 8 Using metal tongs remove the test tube and sample and weigh

ANswer the following questions using the data provided on this page.

1) What is the mass of copper oxide?
2) What is the mass of copper metal present after reaction?
3) What was the mass of oxygen present in the sample of copper oxide?
4) Determine the amount of copper in mol.
5) Determine the amount of oxygen in mol.
6) Knowing that the other products of the above reaction are water and carbon dioxide write a balanced chemical equation for the reaction.
7) From your calculations determine whether the copper oxide used was copper(II)oxide or copper(I)oxide. Show all working out.
8) What happens to the accuracy of our results as we use smaller quantities of copper oxide?