Electrode Potentials and Electrochemical Cells Exam-style MCQs | A-Level Chemistry AQA

Question 1

Which is a redox reaction?

A

Cr₂O₇^2- + 2C ➔ Cr₂O₃ + CO₃^2- + CO

B

CrO₂Cl₂ + 4OH^- ➔ CrO₄^2- + 2Cl^- + 2H₂O

C

Cr₂O₇^2- + 2HCl ➔ 2CrO₃Cl^- + H₂O

D

2CrO₄^2- + 2H⁺ ➔ Cr2O₇^2- + H₂O

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Question 2

The standard reduction potentials of two systems are

Sn⁴⁺_(aq) + 2e^- ⇌ Sn²⁺_(aq) E^⦵ = +0.15 V

Fe³⁺_(aq) + e^- ⇌ Fe²⁺_(aq) E^⦵ = +0.77 V

What is the value of E^⦵_cell for the system below?

Sn⁴⁺_(aq) + 2Fe²⁺_(aq) ➔ Sn²⁺_(aq) + 2Fe³⁺_(aq)

A

-1.39 V

B

-0.62 V

C

+0.62 V

D

+1.39 V

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Question 3

In a hydrogen-oxygen fuel cell, the oxygen is

A

oxidised at the negative electrode

B

oxidised at the positive electrode

C

reduced at the negative electrode

D

reduced at the positive electrode

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Question 4

The reaction between acidified dichromate(VI) ions, Cr₂O₇^2-, and aqueous Fe²⁺ ions results in the dichromate(VI) ions being reduced to Cr³⁺ ions.

What is the correct equation for this reaction?

A

Cr₂O₇^2- + Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + Fe³⁺ + 7H₂O

B

Cr₂O₇^2- + 2Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + 2Fe³⁺ + 7H₂O

C

Cr₂O₇^2- + 3Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + 3Fe³⁺ + 7H₂O

D

Cr₂O₇^2- + 6Fe²⁺ + 14H⁺ ➔ 2Cr³⁺ + 3Fe³⁺ + 6H₂O

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Question 5

The acid used in a standard hydrogen electrode to provide a 1 mol dm^-3 solution of hydrogen ions is

A

ethanoic acid

B

phosphoric(V) acid

C

sulfuric acid

D

hydrochloric acid

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Question 6

To measure the standard electrode potential for the Ag⁺_(aq)| Ag_(s) electrode, the most suitable chemical for the solution in a salt bridge to connect the two half cells is

A

potassium chloride

B

potassium iodide

C

potassium nitrate

D

potassium sulfate

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Question 7

An electrochemical cell consists of a standard hydrogen electrode and a Cu²⁺_(aq)| Cu_(s) electrode which uses copper(II) sulfate solution.

Which one of the following does not affect the e.m.f. of the cell?

A

the volume of the copper(II) sulfate solution

B

the temperature

C

the pressure of the hydrogen

D

the concentration of the copper(II) sulfate solution

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Question 8

The standard electrode potentials of two half reactions are shown below.

$\frac{1}{2}$ Cl₂+ e^- ⇌ Cl^- E^⦵ = +1.36 V

Co³⁺ + e^- ⇌ Co²⁺ E^⦵ = +1.82 V

Which of the following processes is thermodynamically favourable? The reaction of

A

Co²⁺ with Cl₂to form Cl^-

B

Co²⁺ with Cl^-to form Cl₂

C

Co³⁺ with Cl₂to form Cl^-

D

Co³⁺ with Cl^-to form Cl₂

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Question 9

A solution of potassium manganate(VII) was used to determine the concentration of iron(II) ions in solution by titration in the presence of excess dilute sulfuric acid.

With the potassium manganate(VII) in the burette, the end-point of the reaction is when the solution in the conical flask turns

A

colourless

B

pink

C

green

D

orange

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Question 10

Which of the statements about a standard hydrogen electrode, for which E^⦵ = 0 V, is correct?

A

a suitable solution for use in the electrode is hydrochloric acid with a concentration of 0.1 mol dm^-3

B

the pressure of the hydrogen has no effect on the value of E^⦵

C

the metal used in the electrode is platinum

D

the temperature is 273 K

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Question 11

The table below gives the standard electrode potentials of three half cells.

From these data it may be deduced that, under standard conditions,

A

Ag is a stronger reducing agent than H₂

B

Ag²⁺ ions are stronger oxidising agents than H⁺ ions

C

Ag⁺ ions will disproportionate

D

Ag⁺ ions will react with H⁺ ions

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Question 12

Which of the following statements about fuel cells is not true?

A

reactants must constantly be fed into the cell when it is in use

B

fuel cells are 100% efficient

C

fuel cells convert chemical energy directly into electrical energy

D

fuel cells produce electricity more efficiently than a diesel generator

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Question 13

A student is given the electrode potentials below.

Cu²⁺ + 2e^- ⇌ Cu E^⦵ = +0.34 V

Ag⁺ + e^- ⇌ Ag E^⦵ = +0.80 V

The student sets up a cell from the two half cells.

Which statement is correct?

A

the cell voltage is 1.14 V

B

Cu²⁺ is reduced by Ag

C

Cu is oxidised by Ag⁺

D

Cu²⁺ is oxidised by Ag

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Question 14

The redox equilibria for a hydrogen-oxygen fuel cell in alkaline solution are shown below.

2H₂O_(l) + 2e^- ⇌ H_2(g) + 2OH^-_(aq) E^⦵ = –0.83 V

$\frac{1}{2}$ O_2(g) + H₂O_(l) + 2e^- ⇌ 2OH^-_(aq) E^⦵ = +0.40 V

What is the equation for the overall cell reaction?

A

H_2(g) + 4OH^-_(aq) ➔ 3H₂O_(l) + 0.5O_2(g)

B

3H₂O_(l) + 0.5O₂➔ H_2(g) + 4OH^-_(aq)

C

H₂O_(l) ➔ H_2(g) + 0.5O_2(g)

D

H_2(g) + 0.5O_2(g) ➔ H₂O_(l)

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Question 15

The following cell has an e.m.f. of +0.46 V.

Cu | Cu²⁺ || Ag⁺ | Ag

Which statement is correct about the operation of the cell?

A

metallic copper is oxidised by Ag⁺ ions

B

the silver electrode has a negative polarity

C

the silver electrode gradually dissolves to form Ag⁺ ions

D

electrons flow from the silver electrode to the copper electrode via an external circuit

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Question 16

The values for two electrodes are shown.

Fe²⁺_(aq) + 2e^- ⇌ Fe_(s) E^⦵ = -0.44 V

Cu²⁺(aq) + 2e^- ⇌ Cu_(s) E^⦵= +0.34 V

What is the e.m.f. of the cell Fe_(s)| Fe²⁺_(aq)|| Cu²⁺_(aq)| Cu_(s)?

A

+0.78 V

B

+0.10 V

C

-0.10 V

D

-0.78 V

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