Figure 1 represents the cell used to measure the standard electrode potential for the Fe²⁺/Fe electrode - AQA - A-Level Chemistry - Question 3 - 2019 - Paper 3
Question 3
Figure 1 represents the cell used to measure the standard electrode potential for the Fe²⁺/Fe electrode.
0 3.1 Name the piece of apparatus labelled A.
0 3.2 State ... show full transcript
Worked Solution & Example Answer:Figure 1 represents the cell used to measure the standard electrode potential for the Fe²⁺/Fe electrode - AQA - A-Level Chemistry - Question 3 - 2019 - Paper 3
Step 1
Name the piece of apparatus labelled A.
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Answer
The piece of apparatus labelled A is a salt bridge.
Step 2
State the purpose of A.
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Answer
The purpose of A (the salt bridge) is to complete the circuit by allowing the flow of ions, which maintains electrical neutrality in the cell.
Step 3
Name the substance used as electrode B in Figure 1.
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Answer
Electrode B is made of platinum.
Step 4
Complete Table 1 to identify C, D and E from Figure 1. Include the essential conditions for each.
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Answer
Identity
Conditions
C
1 mol dm⁻³
D
100 kPa
E
1 mol dm⁻³
Step 5
Give the ionic equation for the overall reaction in Figure 1.
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Answer
The ionic equation for the overall reaction in Figure 1 is:
ightleftharpoons ext{Fe}$$
Step 6
State the change that needs to be made to the apparatus in Figure 1 to allow the cell reaction to go to completion.
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Answer
To allow the cell reaction to go to completion, the solution in the cell must be changed to maintain the concentration of reactants or remove products.
Step 7
Complete Table 2 to show the value missing from experiment 4.
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Answer
Experiment
[Zn²⁺] mol dm⁻³
[Cu²⁺] mol dm⁻³
Ecell / V
4
1.00
0.00
1.04
Step 8
Calculate the gradient of your plotted line on the graph in question 0 3.6.
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Answer
The gradient of the plotted line should be calculated based on the derived points from the graph, which will yield a value of approximately -0.013 V.
Step 9
Use your gradient to calculate the temperature, T, at which the measurements of Ecell were taken.
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Answer
Using the gradient value in the equation:
Ecell=(−4.3imes10−5imesT)+E°cell
we can rearrange to find T. Given the gradient is -0.013 V, we set the equation to find T:
T = rac{E° - E_{cell}}{-4.3 imes 10^{-5}}
Using the value -0.013, we would find T to be approximately 302.0 K.
Step 10
Calculate the electrode potential for the Zn²⁺/Zn electrode in experiment 2.
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Answer
For experiment 2:
EZn2+/Zn=Ecell−ECu2+/Cu
Substituting the values gives:
EZn2+/Zn=1.04V−0.33V=0.71V
Step 11
Give one reason why your calculated value is different from the standard electrode potential for Zn²⁺/Zn electrode.
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Answer
The calculated value may differ from the standard electrode potential due to varying concentration conditions in the experiment compared to standard conditions.
