Electrode Potentials Exam-style MCQs | A-Level Chemistry OCR

Question 1

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

0

/

1

Question 2

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

0

/

1

Question 3

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

0

/

1

Question 4

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

0

/

1

Question 5

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

0

/

1

Question 6

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

0

/

1

Question 7

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

0

/

1

Question 8

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

0

/

1

Question 9

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

0

/

1

Question 10

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

0

/

1

Question 11

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)

0

/

1

Question 12

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

0

/

1

Question 13

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

0

/

1