A student set up the cell shown in Figure 2 - AQA - A-Level Chemistry - Question 6 - 2018 - Paper 1
Question 6
A student set up the cell shown in Figure 2.
Figure 2
Copper
0.15 mol dm$^{-3}$ CuSO$_4$(aq)
Copper
1.0 mol dm$^{-3}$ CuSO$_4$(aq)
The student recorded an init... show full transcript
Worked Solution & Example Answer:A student set up the cell shown in Figure 2 - AQA - A-Level Chemistry - Question 6 - 2018 - Paper 1
Step 1
Explain how the salt bridge provides an electrical connection between the two solutions.
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Answer
The salt bridge contains mobile ions that can move through it, allowing the flow of ions between the two solutions. This maintains electrical neutrality and allows the circuit to complete, preventing the buildup of charge.
Step 2
Calculate the electrode potential of the left-hand electrode in Figure 2.
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Answer
The electrode potential of the left-hand electrode can be determined using the Nernst equation, taking into consideration the concentration of the copper ions in the solution. Given that the concentration is not +0.34 V, we recognize that...
Electrode potential = +0.16 V.
Step 3
State why the left-hand electrode does not have an electrode potential of +0.34 V.
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Answer
The left-hand electrode does not have an electrode potential of +0.34 V because the concentration of Cu2+ ions in this electrode is lower than that at standard conditions (1.0 mol dm−3).
Step 4
Give the conventional representation for the cell in Figure 2.
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Suggest how the concentration of copper(II) ions in the left-hand electrode changes when the bulb is alight.
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Answer
When the bulb is alight, the concentration of copper(II) ions in the left-hand electrode decreases as copper ions are reduced and deposit as solid copper on the cathode.
Step 6
Give one reason why the EMF of the cell decreases to 0 V.
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The EMF decreases to 0 V because the concentration of copper(II) ions in the two solutions becomes equal, leading to no further potential difference between the electrodes.
