Chapter Four · 1- Galvanic cells: practice questions

In an operating galvanic cell, reduction of the positive ions takes place at one of the two electrodes. This electrode is:

• Athe cathode, which is the positive electrode.
• Bthe anode, which is the positive electrode.
• Cthe anode, which is the negative electrode.
• Dthe cathode, which is the negative electrode.

What happens to the primary cells when the anode material is consumed and the ions of the cathode half-cell are diminished?

• AThey can be recharged by an external direct current source.
• BTheir electrolyte concentration is renewed automatically.
• CThey convert into secondary storage batteries.
• DThey stop to work as they are irreversible cells.

When two metals of different standard reduction potentials are combined to form a galvanic cell, the electrode that behaves as the cathode is the one having the:

• ALower (more negative) standard reduction potential.
• BLarger mass of metal.
• CGreater tendency to be oxidised.
• DHigher (more positive) standard reduction potential.

A clean strip of zinc is placed in copper(II) sulphate solution. Given E°(Zn²⁺/Zn) = -0.76 V and E°(Cu²⁺/Cu) = +0.34 V, which of the following is correct?

• ANo reaction occurs because zinc is less active than copper.
• BCopper is deposited only after the solution is heated because the reaction is non-spontaneous.
• CZinc displaces copper because zinc is the stronger reducing agent, and the reaction is spontaneous.
• DCopper displaces zinc from the metal strip, forming zinc metal.

Which of the following describes the components of the mercury cell poles and its electrolyte?

• AZinc anode, mercury oxide positive pole, and potassium hydroxide electrolyte.
• BLithium graphite anode, lithium cobalt oxide cathode, and LiPF6 electrolyte.
• CLead anode, lead dioxide cathode, and sulphuric acid electrolyte.
• DPorous carbon anode, porous carbon cathode, and hydrated potassium hydroxide.

A galvanic cell is formed from a nickel electrode and a silver electrode. Given E°(Ag⁺/Ag) = +0.80 V and E°(Ni²⁺/Ni) = -0.25 V, the standard e.m.f. of the cell equals:

• A+1.05 V
• B+0.55 V
• C-1.05 V
• D-0.55 V

Based on the electromotive series, which elements are considered good reducing agents?

• AThe elements at the front of the series having high oxidation potential
• BThe elements at the end of the series having high reduction potential
• CThe elements that have a standard reduction potential of exactly zero
• DThe elements that do not react with hydrochloric acid

A galvanic cell is constructed from an aluminium electrode (E° = -1.66 V) and a zinc electrode (E° = -0.76 V) under standard conditions. Which of the following correctly identifies the anode and gives the standard e.m.f. of the cell?

• AAluminium is the anode and the e.m.f. = +2.42 V
• BZinc is the anode and the e.m.f. = -0.90 V
• CZinc is the anode and the e.m.f. = +0.90 V
• DAluminium is the anode and the e.m.f. = +0.90 V

Three metals A, B and C have standard reduction potentials A = -0.76 V, B = +0.34 V and C = -0.44 V. If three galvanic cells are made from the pairs (A, B), (B, C) and (A, C), which pair produces the cell with the greatest standard e.m.f.?

• AThe pair (A, B), with e.m.f. = +1.10 V
• BThe pair (A, C), with e.m.f. = +0.32 V
• CThe pair (B, C), with e.m.f. = +0.78 V
• DThe pair (A, B), with e.m.f. = +0.42 V

In an electrolytic cell, why is the oxidation process forced to occur at the anode despite it being a non-spontaneous reaction?

• ABecause the anode has a higher reduction potential than the cathode.
• BBecause the external power source pulls electrons from the anode.
• CBecause the salt bridge forces the flow of positive ions to the anode.
• DBecause the electrolytic solution is inherently unstable.