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When copper sulfate solution is electrolysed using copper electrodes, the mass of each electrode changes - Edexcel - GCSE Chemistry - Question 5 - 2022 - Paper 1
Question 5
When copper sulfate solution is electrolysed using copper electrodes, the mass of each electrode changes. (a) Draw a labelled diagram to show the apparatus that can... show full transcript
Worked Solution & Example Answer:When copper sulfate solution is electrolysed using copper electrodes, the mass of each electrode changes - Edexcel - GCSE Chemistry - Question 5 - 2022 - Paper 1
Step 1
Draw a labelled diagram to show the apparatus that can be used to electrolyse copper sulfate solution using copper electrodes.
Answer
To demonstrate the apparatus used for electrolysis, draw a beaker containing copper sulfate solution with two copper electrodes inserted. Label the components:
- Beaker
- Copper electrodes (anode and cathode)
- Power supply (DC) connected to electrodes
Step 2
Explain what should be done to the copper electrodes before their masses are determined.
Answer
Before measuring the mass of each copper electrode, the electrodes should be carefully scrubbed using emery paper or a similar abrasive material to remove any surface contaminants, such as oxide layers or other impurities. This ensures accurate mass measurements.
Step 3
Explain, in terms of ions, the changes in mass of the two electrodes shown in the results in Figure 4.
Answer
During the electrolysis of copper sulfate, the anode loses mass due to the oxidation of copper atoms into copper ions:
ext{Cu (s) }
ightarrow ext{ Cu}^{2+} (aq) + 2e^{-}
Thus, the anode's mass decreases by 0.81g. Conversely, at the cathode, copper ions in the solution gain electrons and are deposited as solid copper:
ext{Cu}^{2+} (aq) + 2e^{-}
ightarrow ext{Cu (s)}
This increases the cathode's mass by 0.78g.
Step 4
Explain a change that could be made to the electrolysis experiment to cause the mass of the cathode to increase by 2.34g in 10 minutes.
Answer
To increase the mass of the cathode significantly, you could increase the current used in the electrolysis process. This is achieved by either using a greater surface area for the electrodes or adjusting the voltage to enhance the current, leading to an increased rate of copper ion deposition at the cathode.