10-minute Quiz : Chapter 31 Redox reactions in chemical cells

Which of the following statements concerning the cathode of a chemical cell is correct?

• A. Oxidation occurs at the cathode.
• B. Electrons move into the cathode.
• C. It is the negative electrode.
• D. It must be an inert electrode.

For which of the following half cell reactions is independent of the pH of the solution?

• A. Co²⁺ + 2e⁻ ⇌ Co

• B. H₂O₂ + 2H⁺ + 2e⁻ ⇌ 2H₂O

• C. NO₃⁻ + H₂O + 2e⁻ ⇌ NO₂⁻ + 2OH⁻

• D. Cr₂O₇²⁻ + 14H⁺ + 6e⁻ ⇌ 2Cr³⁺ + 7H₂O

The diagram shows a chemical cell connected to a voltmeter. It is known that iron is a stronger reducing agent than nickel. Which of the following statements is INCORRECT?

• A. Electrons flow from iron to nickel in the external circuit.
• B. The colour of the nickel(II) nitrate solution fades.
• C. The colour of the iron(II) sulphate solution changes from green to yellow.
• D. Reduction takes place at the nickel electrode.

Which of the following substances can be used as a fuel in a fuel cell?

• A. Nitrogen
• B. Oxygen
• C. Methanol
• D. Helium

The diagram shows a standard hydrogen electrode. Which of the following equations represents the reduction occurred in the standard hydrogen electrode when it acts as a cathode?

• A. H₂(g) → 2H⁺(aq) + 2e⁻
• B. H⁺(aq) + OH⁻(aq) → H₂O(l)
• C. O₂(g) + 4H⁺(aq) + 4e⁻ → 2H₂O(l)
• D. 2H⁺(aq) + 2e⁻ → H₂(g)

A simple chemical cell is connected to a voltmeter as shown in the diagram. Which of the following statements concerning the chemical cell is INCORRECT?

• A. Colourless gas bubbles evolve at graphite electrode A.

• B. The purple solution in the right half cell gradually fades.
• C. The salt bridge can be prepared by soaking a strip of filter paper with CaCl₂(aq).
• D. Graphite electrode B is the cathode.

The following equation represents the overall reaction occurred in a chemical cell.

Mg(s) + Cu²⁺(aq) → Mg²⁺(aq) + Cu(s)

Which of the following statements must be correct?

(1) The anode of the chemical cell is made of magnesium.

(2) The cathode of the chemical cell is made of copper.

(3) Magnesium is the reducing agent.

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

In a hydrogen-oxygen fuel cell,

• A. hydrogen loses electrons at the positive electrode.
• B. potassium ions gain electrons at the anode.
• C. water forms in the cathode compartment.
• D. oxygen is reduced at the cathode.

Which of the following is/are the drawback(s) of using hydrogen-oxygen fuel cells?

(1) There is a risk of leakage of flammable hydrogen gas.

(2) The use of hydrogen-oxygen fuel cells produces many air pollutants.

(3) The energy conversion efficiency of hydrogen-oxygen fuel cells is low.

• A. (1) only
• B. (2) only
• C. (1) and (3) only
• D. (2) and (3) only

Consider the following statements and choose the best answer:

1st statement

Platinum electrodes are used as inert electrodes in chemical cells.

2nd statement

Platinum is an unreactive metal.

• A. Both statements are true and the 2nd statement is a correct explanation of the 1st statement.
• B. Both statements are true but the 2nd statement is NOT a correct explanation of the 1st statement.
• C. The 1st statement is false but the 2nd statement is true.
• D. Both statements are false.