3.1.11 Electrode potentials + electrochemical cells (A-level only)

Which ion cannot catalyse the reaction between iodide (I^–) and peroxodisulfate (S₂O₈^2–)?

Use the data in the table to help you answer this question.

• Co²⁺

• Cr²⁺

• Fe²⁺

• Fe³⁺

The following cell has an EMF of +0.46 V.

Cu | Cu²⁺ || Ag⁺ | Ag

Which statement is correct about the operation of the cell?

• Metallic copper is oxidised by Ag⁺ ions.

• The silver electrode has a negative polarity.

• The silver electrode gradually dissolves to form Ag⁺ ions.

• Electrons flow from the silver electrode to the copper electrode via an external circuit.

In this question consider the data in the image.

The e.m.f. of the cell Ag(s) | Ag⁺(aq) || Pb²⁺(aq) | Pb(s) is

• 0.93 V

• 0.67 V

• −0.67 V

• −0.93 V

In this question consider the data in the image.

The e.m.f. of the cell Pt(s) | H₂(g) | H⁺(aq) || Ag⁺(aq) | Ag(s) would be increased by

• increasing the concentration of H⁺(aq).

• increasing the surface area of the Pt electrode.

• increasing the concentration of Ag⁺(aq).

• decreasing the pressure of H₂(g).

A disproportionation reaction occurs when a species M⁺ spontaneously undergoes simultaneous oxidation and reduction.

2M⁺(aq) → M²⁺(aq) + M(s)

The table contains E^⦵ data for copper and mercury species.

Using these data, which one of the following can be predicted?

• Both Cu(I) and Hg(I) undergo disproportionation.

• Only Cu(I) undergoes disproportionation.

• Only Hg(I) undergoes disproportionation.

• Neither Cu(I) nor Hg(I) undergoes disproportionation.

Based on the above data, which one of the following could reduce 0.012 mol of bromine to bromide ions?

• 40 cm³ of a 0.10 mol dm⁻³ solution of Cr₂O₇^2- (aq)

• 80 cm³ of a 0.30 mol dm⁻³ solution of Fe³⁺(aq)

• 50 cm³ of a 0.24 mol dm⁻³ solution of V³⁺(aq)

• 50 cm³ of a 0.24 mol dm⁻³ solution of H₂SO₃(aq)

Use the data in the table to answer this question.

The most powerful oxidising agent in the table is

• Mn²⁺(aq)

• Zn(s)

• MnO₄^-(aq)

• Zn²⁺(aq)

Use the data in the table to answer this question.

Which one of the following statements is not correct?

• Fe²⁺(aq) can reduce acidified MnO₄^-(aq) to Mn²⁺(aq)

• CrO₇^2-(aq) can oxidise acidified Fe²⁺(aq) to Fe³⁺(aq)

• Zn(s) can reduce acidified CrO₇^2-(aq) to Cr²⁺(aq)

• Fe²⁺(aq) can reduce acidified Cr³⁺(aq) to Cr²⁺(aq)