AQA A Level Chemistry

Topic Questions

5.4 Electrode Potentials & Electrochemical Cells (A Level only)

11 mark

Which is the correct equation to calculate electromotive force?

  • EӨcell = EӨreduction + EӨoxidation

  • EӨcell = EӨreductionEӨoxidation

  • EӨcell = EӨhydrogen + EӨreduction  

  • EӨcell = EӨoxidationEӨreduction

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21 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

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.

5-4-aqa-a-level-chemistry-mcq-q4-hard

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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11 mark

The electrochemical cell that is used to measure the standard electrode potential of the Cu2+ / Cu electrode is:

5-4-aqa-a-level-chemistry-mcq-q1-medium

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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