11 mark
Which is the correct equation to calculate electromotive force?
EӨcell = EӨreduction + EӨoxidation
EӨcell = EӨreduction – EӨoxidation
EӨcell = EӨhydrogen + EӨreduction
EӨcell = EӨoxidation – EӨreduction
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Electrode Potentials & Electrochemical Cells (AQA A Level Chemistry)
Exam Questions
3 hours30 questions21 mark
An electrochemical cell is established using the half cells described.
Oxidation half-cell | Reduction half-cell |
Iron electrode in 1.0 mol dm-3 iron(II) sulfate solution | Copper electrode in 1.0 mol dm-3 copper(II) sulfate solution |
Which of the following is the correct conventional representation for the electrochemical cell formed?
Fe (s) | Fe3+ (aq) || Cu2+ (aq) | Cu (s)
Fe2+ (aq) | Fe (s) || Cu2+ (aq) | Cu (s)
Cu (s) | Cu2+ (aq) || Fe2+ (aq) | Fe (s)
Fe (s) | Fe2+ (aq) || Cu2+ (aq) | Cu (s)
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31 mark
The EΘ values for two electrodes are shown.
Fe3+ (aq) + e– ⇌ Fe2+ (aq) EΘ = +0.77 V
Co3+ (aq) + e– ⇌ Co2+ (aq) EΘ = +1.82 V
What is the EMF of the cell Fe2+ (aq) | Fe3+ (aq) || Co3+ (aq) | Co2+ (aq)?
+2.59 V
+1.05 V
-1.05 V
-2.59 V
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41 mark
Use the data below to help you answer this question.
Half-equation | EO / V |
Co3+ (aq) + e– ⇌ Co2+ (aq) | +1.82 |
Cr3+ (aq) + e– ⇌ Cr2+ (aq) | –0.41 |
Fe3+ (aq) + e– ⇌ Fe2+ (aq) | +0.77 |
S2O82– (aq) + 2e– ⇌ 2SO42– (aq) | +2.01 |
Which is the most powerful oxidising agent from all the species in the table?
Co3+ (aq)
Cr3+ (aq)
Fe3+ (aq)
SO42– (aq)
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51 mark
Which of the following is true about the role of the salt bridge in an electrochemical cell?
It must not contain an ion found in the half cells
It must be a nitrate salt
It must enable ions to flow between the oxidation and reduction half-cell
It must allow electrons to flow around the circuit
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11 mark
The electrochemical cell that is used to measure the standard electrode potential of the Cu2+ / Cu electrode is:
Which label is wrong in the diagram?
Pt (s)
1 mol dm-3 HCl (aq)
1 mol dm-3 CuSO4 (aq)
Pt (s)
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21 mark
Which of the following statements is not correct?
The standard hydrogen electrode has a standard electrode potential value of 1.00 V
By convention, the standard hydrogen electrode is always the oxidation reaction
Electromotive force values are positive
By convention, the right hand electrode of an electrochemical cell is where reduction occurs
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31 mark
Some standard electrode potential data is shown in the table.
Electrode half-equation | EӨ / V |
Fe3+ + e− ⇋ Fe2+ | +0.77 |
Cu2+ + 2e- ⇋ Cu | +0.34 |
2H+ + 2e− ⇋ H2 | 0.00 |
Fe2+ + 2e− ⇋ Fe | -0.44 |
The electromotive force for the Fe (s) | Fe2+ (aq) | | Cu2+ (aq) | Cu (s) cell is
+0.78 V
-0.10 V
+0.43 V
-0.78 V
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41 mark
Some standard electrode potential data is shown in the table.
Electrode half-equation | EӨ / V |
BrO- + H2O + 2e- ⇋ Br- + 2OH– | +0.76 |
2NH4+ + 2e– ⇋ 2NH3 + H2 | +0.74 |
Cu2+ + 2e- ⇋ Cu | +0.34 |
Pb2+ + 2e- ⇋ Pb | -0.36 |
Zn2+ + 2e- ⇋ Zn | -0.76 |
The Daniell cell is non-rechargeable and has an electromotive force of +1.10 V. One half cell is Cu2+ / Cu.
What is the other half cell?
BrO- / Br -
Zn2+ / Zn
NH4+ / NH3
Pb2+ / Pb
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51 mark
Which statements about the different systems used in batteries / cells are correct?
| Lead-acid | Nickel-cadmium | Hydrogen-oxygen |
A | Fuel | Rechargeable | Fuel |
B | Rechargeable | Fuel | Rechargeable |
C | Fuel | Fuel | Rechargeable |
D | Rechargeable | Rechargeable | Fuel |
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11 mark
Some standard electrode potential data is shown in the table.
Electrode half-equation | EӨ / V |
Co3+ (aq) + e– → Co2+(aq) | +1.82 |
Cu2+ (aq) + 2e- ⇋ Cu (s) | +0.34 |
Fe3+ (aq) + e– → Fe2+(aq) | +0.77 |
I2 (s) + 2e– → 2I– (aq) | +0.54 |
S2O82– (aq) + 2e– → 2SO42– (aq) | +2.01 |
Which species cannot catalyse the reaction between iodide ions, I– (aq), and peroxodisulfate ions, S2O82– (aq)?
Co2+
Cu2+
Fe3+
Fe2+
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21 mark
The following electrochemical cell has an electromotive force of +2.46 V.
Al (s) | Al 3+ (aq) || Ag+ (aq) | Ag (s)
Which statement about the operation of the cell is not correct?
The mass of the silver electrode increases during the cell’s operation
The silver electrode has a positive polarity
The aluminium electrode is reduced by Ag+ ions
Electrons flow from the aluminium electrode to the silver electrode via an external circuit
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31 mark
Some standard electrode potential data is shown in the table.
Electrode half-equation | EӨ / V |
Ag+ (aq) + e- ⇌ Ag (s) | +0.80 |
Al3+ (aq) + 3e- ⇌ Al (s) | -1.66 |
Cl2 (g) + 2e- ⇌ 2Cl - (aq) | +1.36 |
ClO2 (aq) + e- ⇌ ClO2- (aq) | +0.95 |
Cu2+ (aq) + 2e- ⇌ Cu (s) | +0.34 |
Pb4+ (aq) + 2e- ⇌ Pb2+ (aq) | +1.67 |
Which is the correct cell representation for the electrochemical cell with an electromotive force of +0.87 V?
Ag (s) | Ag+ (aq) | | Pb4+ (aq) , Pb2+ (aq)
Pb4+ (aq) | Pb2+ (aq) | | Ag (s) | Ag+ (aq)
Pt (s) | Pb2+ (aq) , Pb4+ (aq) | | Ag+ (aq) | Ag (s)
Ag (s) | Ag+ (aq) | | Pb4+ (aq) , Pb2+ (aq) | Pt (s)
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41 mark
The Daniell cell is shown in the following diagram.
Which statement is correct about the Daniell cell?
The reduction reaction that occurs is Zn2+ (aq) + 2e- → Zn (s)
The reduction reaction that occurs is Cu2+ (aq) + 2e- → Cu (s)
The porous pot allows electrons to flow
The mass of zinc metal in the cell will increase
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51 mark
What happens to the hydrogen in a hydrogen-oxygen fuel cell?
It is oxidised at the cathode
It is reduced at the cathode
It is oxidised at the anode
It is reduced at the anode
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