Figure 1 represents the cell used to measure the standard electrode potential for the Fe<sup>3+</sup>/Fe<sup>2+</sup> 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 Fe<sup>3+</sup>/Fe<sup>2+</sup> electrode.
0.3.1 Name the piece of apparatus l... show full transcript
Worked Solution & Example Answer:Figure 1 represents the cell used to measure the standard electrode potential for the Fe<sup>3+</sup>/Fe<sup>2+</sup> 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 is to complete the circuit by allowing the flow of ions between the two half-cells.
Step 3
Name the substance used as electrode B in Figure 1.
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Answer
Electrode B is a platinum electrode.
Step 4
Complete Table 1 to identify C, D and E from Figure 1. Include the essential conditions for each.
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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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The change needed is to replace the hydrogen gas used in electrode C with additional zinc ions to ensure sufficient concentration for the reduction reaction.
Step 7
Complete Table 2 to show the value missing from experiment 4.
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Answer
For experiment 4, the missing value is [Cu<sup>2+</sup>] = 0.00 mol dm<sup>-3</sup>, E<sub>cell</sub> = 1.04 V.
Step 8
Plot a graph of E<sub>cell</sub> against ln([Zn<sup>2+</sup>]/[Cu<sup>2+</sup>]).
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Answer
Plot the E<sub>cell</sub> values against ln([Zn<sup>2+</sup>]/[Cu<sup>2+</sup>]) values on a graph with appropriate labeling.
Step 9
Calculate the gradient of your plotted line on the graph in question 0.3.6.
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Answer
The calculated gradient from the graph is approximately -0.013 V.
Step 10
Use your gradient to calculate the temperature, T.
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Answer
Using the gradient, the temperature T can be calculated as T = -0.43/(gradient) = 302 K.
Step 11
Use data from Table 2 in question 0.3.6 to calculate the electrode potential for the Zn<sup>2+</sup>/Zn electrode in experiment 2.
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Answer
The electrode potential for the Zn<sup>2+</sup>/Zn electrode in experiment 2 is calculated to be E<sub>Zn</sub> = 0.80 V.
Step 12
Give one reason why your calculated value is different from the standard electrode potential for Zn<sup>2+</sup>/Zn electrode.
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The calculated value may differ due to non-standard conditions such as differing concentrations or temperature affecting the electrode potential.
