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.
**03.1** Name the piece of apparatus labelled A.
**03.2** ... 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.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The piece of apparatus labelled A is a salt bridge.
Step 2
State the purpose of A.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The purpose of A is to complete the circuit by allowing the flow of ions to maintain electrical neutrality in the cell.
Step 3
Name the substance used as electrode B in Figure 1.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The substance used as electrode B is platinum.
Step 4
Complete Table 1 to identify C, D and E from Figure 1. Include the essential conditions for each.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Identity
Conditions
C
HCl (1 mol dm⁻³)
D
H₂ (100 kPa)
E
Fe²⁺ (1 mol dm⁻³)
Step 5
Give the ionic equation for the overall reaction in Figure 1.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The ionic equation for the overall reaction is:
ightarrow 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.
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To allow the cell reaction to go to completion, a platinum electrode can be added to facilitate the transfer of electrons.
Step 7
Complete Table 2 to show the value missing from experiment 4.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The missing value in Table 2 for experiment 4 is:
[extZn2+]extmoldm−3=1.00
Step 8
Plot a graph of Ecell against ln([Zn²⁺]/[Cu²⁺]) on the grid.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
To plot the graph, use the values from Table 2. The y-axis will be Ecell (V) and the x-axis will be ln([Zn²⁺]/[Cu²⁺]). Ensure proper scaling on both axes.
Step 9
Calculate the gradient of your plotted line on the graph in question 03.6.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The gradient calculated from the plotted line is -0.013 V.
Step 10
Use your gradient to calculate the temperature, T, at which the measurements of Ecell were taken.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Using the formula, T = (E°cell - Ecell)/(-4.3 × 10⁻⁵), we find that T = 302 °C or T = 575 K.
Step 11
Calculate the electrode potential for the Zn²⁺/Zn electrode in experiment 2.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
From the data in Table 2, the calculated electrode potential for the Zn²⁺/Zn electrode is -0.80 V.
Step 12
Give one reason why your calculated value is different from the standard electrode potential for Zn²⁺/Zn electrode.
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The calculated value may differ from the standard electrode potential due to non-standard conditions such as changes in concentration or temperature affecting the cell's performance.
