The electrochemical cell below is set up to demonstrate the purification of copper - NSC Physical Sciences - Question 9 - 2016 - Paper 2
Question 9
The electrochemical cell below is set up to demonstrate the purification of copper.
The graphs below show the change in mass of the electrodes whilst the cell is in... show full transcript
Worked Solution & Example Answer:The electrochemical cell below is set up to demonstrate the purification of copper - NSC Physical Sciences - Question 9 - 2016 - Paper 2
Step 1
Write down the type of electrochemical cell illustrated above.
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Answer
The type of electrochemical cell illustrated above is an electrolytic cell.
Step 2
Define a reducing agent in terms of electron transfer.
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Answer
A reducing agent is a substance that loses electrons during a chemical reaction and, in doing so, causes the reduction of another substance. It is therefore considered to be the electron donor.
Step 3
Which graph represents the change in mass of electrode A?
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Answer
The graph labeled P represents the change in mass of electrode A. In an electrolytic cell, the anode (where oxidation occurs) experiences a decrease in mass while the cathode (where reduction occurs) experiences an increase.
Step 4
Write down the half-reaction that takes place at electrode A.
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Answer
At electrode A, the half-reaction is as follows:
ightarrow Cu^{2+}(aq) + 2e^-$$
This indicates that solid copper loses two electrons and goes into the solution as copper ions.
Step 5
At which electrode (A or B) is chlorine gas (Cl₂) formed? Fully explain how it is.
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Answer
Chlorine gas (Cl₂) is formed at electrode B. This occurs because during electrolysis, chloride ions (Cl⁻) are oxidized at the anode ( electrode B), releasing chlorine gas. The chemical reaction can be represented as:
ightarrow Cl_2(g) + 2e^-$$
This explains that the oxidation of chloride ions takes place at electrode B, which leads to the formation of chlorine gas.
