Copper forms two oxides, Cu2O and CuO - AQA - GCSE Chemistry - Question 8 - 2019 - Paper 1
Question 8
Copper forms two oxides, Cu2O and CuO.
A teacher investigated an oxide of copper.
Figure 10 shows the apparatus.
This is the method used.
1. Weigh empty tube A.
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Worked Solution & Example Answer:Copper forms two oxides, Cu2O and CuO - AQA - GCSE Chemistry - Question 8 - 2019 - Paper 1
Step 1
Suggest one reason why step 8 is needed.
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Answer
Step 8 is needed to ensure that all of the oxide of copper has reacted completely. This guarantees that the final mass measurement reflects only the remaining substances, confirming that the reaction has reached completion.
Step 2
Explain why the excess hydrogen must be burned off.
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Answer
Excess hydrogen must be burned off to prevent any unreacted hydrogen from escaping into the atmosphere. Hydrogen is flammable and explosive, so its presence could lead to dangerous conditions during or after the experiment.
Step 3
Determine the mass of copper and the mass of water produced in this experiment.
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Answer
From Table 5:
The mass of tube A and oxide of copper before heating is 115.47 g.
The mass after heating for 2 minutes is 114.62 g.
Mass of copper produced:
Mass before heating - Mass after heating = 115.47 g - 114.62 g = 0.85 g.
Mass of water produced can be found as follows:
Mass of tube B and contents at the start: 120.93 g.
Total mass at the end: 123.38 g.
Mass of water = Mass of tube B and contents at the end - Mass of tube B and contents at the start = 123.38 g - 120.93 g = 2.45 g.
Thus, the mass of copper is 0.85 g and the mass of water is 2.45 g.
