SK025 CHAPTER 3 ELECTROCHEMISTRY

1. The diagram below shows the electrolysis of concentrated aqueous potassium chloride using platinum electrodes. Which of the following statements is TRUE regarding the electrolysis of concentrated aqueous potassium chloride?

• H₂O is reduced at the cathode due to its more negative E⁰ value than K⁺.
• Cl⁻ is oxidised at the anode due to its more positive E⁰ value than H₂O.
• Cl⁻ ions are oxidised at anode due to higher concentration.
• Platinum is an active electrode.

2. The standard reduction electrode potential for several half-reactions at 298 K are shown below. Which of the following species is the strongest oxidising agent?

• X⁻

• Y³⁺

• Z

• X₂

Answer explanation

strongest oxidising agent -> undergo reduction (gain electron, +SRP value) -> species who gain electron (look at reactant side)

3. According to Faraday's first law, the amount of a substance produced at each electrode in an electrolytic cell is directly proportional to the

• voltage provided
• quantity of electricity passed
• temperature
• concentration of electrolyte

4. What are the features of a standard hydrogen electrode?

I. Hydrogen gas at 1 atm and 298 K

II. A platinum electrode

III. A carbon electrode

IV. 1M aqueous solution of a strong acid

• I, II and III
• I, II and IV
• II, III and IV
• I, II, III and IV

5. The following diagram shows a galvanic cell. Which of the following statements is correct?

• The aluminium electrode is cathode.
• The mass of Pb plate decreases.
• Pb (lead) reduces.
• Aluminium electrode is the negative terminal.

6. 2Ag⁺ (aq) + Mg (s) ⟶ 2Ag (s) + Mg²⁺ (aq)

Calculate E° cell.

[Given E° Ag⁺/Ag = +0.80V and E° Mg²⁺/Mg= - 2.36V ]

• -1.56 V
• -3.16V
• +1.56 V
• +3.16V

7. Explain why a salt bridge is usually necessary for the operation of a galvanic cell

I. To allow the electron to flow from anode to cathode.

II. To complete the circuit

III. To maintain the electrical neutrality of both electrolytes.

• I only
• I and II
• II and III
• I, II and III

8. Standard hydrogen electrode operated under standard conditions of 1 atm H₂ pressure, 25°C, and pH = 0 has a cell potential of

• 0.00 V
• 0.05 V
• 0.10 V
• 0.50 V

9. Electrochemistry is the study of production of electricity from

• nuclear energy and the use of heat energy to bring about non-spontaneous chemical transformations.
• energy released during spontaneous chemical reactions and the use of electrical energy to bring about non-spontaneous chemical transformations.
• nuclear energy and the use of electrical energy to bring about non-spontaneous chemical transformations.
• energy released during spontaneous chemical reactions and the use of heat energy to bring about non-spontaneous chemical transformations.

10. The Nernst equation is used to calculate the cell potential of a galvanic cell under non-standard conditions. Which is the correct expression of Nernst equation for the following reaction? Ni (s) + Cl₂ (g) ⟶ Ni²⁺ (aq) + 2Cl (aq)⁻

• A
• B
• C
• D