This question is about chemical reactions and electricity - AQA - GCSE Chemistry - Question 7 - 2021 - Paper 1

The half equation is:

$ext{Br}^- \rightarrow \text{Br}_2 + 2 e^-$

To find the total mass of copper, the students should filter the mixture, wash and dry the copper residue, weigh the copper collected, and then add this mass to the increase in mass of the electrode.

For a given current, the results show a straight line through the origin, indicating that the total mass of copper produced increases linearly with time. Thus, when the time doubles, the mass of copper produced also doubles, confirming direct proportionality.

The graph shows that for a fixed time, if the current is increased, the mass produced also increases. Specifically, when the current is doubled, the mass doubles, which supports the conclusion of proportionality between mass produced and current.

The blue colour fades because copper ions are discharged from the solution during the electrolysis, leading to a decrease in the concentration of copper ions in the solution.

First, calculate the number of moles of copper produced:

$\text{Number of moles} = \frac{0.24}{63.5} = 0.00378$

Next, calculate the number of atoms:

$\text{Number of atoms} = 0.00378 \times 6.02 \times 10^{23} = 2.28 \times 10^{21}$

Thus, the answer is 2.28 × 10²¹.