Copper forms two oxides, Cu₂O and CuO - AQA - GCSE Chemistry - Question 8 - 2019 - Paper 1

The excess hydrogen must be burned off to prevent it from escaping into the atmosphere, as hydrogen is explosive. This ensures that all the hydrogen has reacted, allowing for accurate measurements in the experiment.

To find the mass of copper and water produced:

• Mass of copper:

  • Mass of tube A after heating: 114.38 g.
  • Initial mass of tube A with oxide of copper: 115.47 g.
  • Mass of copper = 115.47 g - 114.38 g = 1.09 g.

• Mass of water:

  • Mass of tube B at start: 120.93 g.
  • Mass of tube B at end: 123.38 g.
  • Mass of water = 123.38 g - 120.93 g = 2.45 g.

Thus, the results are:

Mass of copper = 1.09 g Mass of water = 2.45 g

To determine the correct equation, we need to analyze the provided data. The teacher found that 2.54 g of copper and 0.72 g of water were produced.

Using the molar mass of water (H₂O, 18 g/mol), the moles of water produced can be calculated:

$moles ext{ of } H_2O = \frac{0.72 ext{ g}}{18 ext{ g/mol}} = 0.04 ext{ mol}$

In both equations:

• For Equation 1: Cu₂O + H₂ → 2 Cu + H₂O

  • 0.04 mol of water corresponding to 0.04 mol of Cu
  • This suggests 0.08 mol of Cu is produced.

• For Equation 2: CuO + H₂ → Cu + H₂O

  • 0.04 mol of water corresponds to 0.04 mol of Cu.

Thus, since the quantity of copper produced (2.54 g) aligns with expected outcomes, Equation 2 (CuO + H₂) is the correct one.