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.
2.... show full transcript
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, confirming that no further changes in mass occur.
Step 2
Explain why the excess hydrogen must be burned off.
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Answer
The excess hydrogen must be burned off to prevent it from escaping into the air, as hydrogen is flammable and poses an explosion risk.
Step 3
Determine the mass of copper and the mass of water produced in this experiment.
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Answer
From Table 5:
Mass of copper = 8.66 g
Mass of water = 2.45 g
Step 4
The teacher repeated the experiment with a different sample of the oxide of copper. Determine which is the correct equation for the teacher’s experiment.
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Answer
To determine the correct equation, we calculate the moles of Cu and H2O:
For Equation 1 (Cu2O):
Moles of Cu = 0.04 (from 2.54 g of copper)
Moles of H2O = 0.04 (from 0.72 g of water)
For Equation 2 (CuO):
Moles of Cu = 0.04 (from 2.54 g of copper)
Moles of H2O: 0.04 (from 0.72 g of water)
Since both equations yield the same ratio of Cu to H2O, we need to analyze the ratio:
For equation 1: Copper to water ratio = 1:1
For equation 2: Copper to water ratio = 1:1
Thus, both equations are valid mathematically; however, the experimental data aligns better with Equation 2, due to the direct formation of water from the reaction of CuO.
