College Chemistry: Electrochemistry - Electrolytic Cells, Electrolysis, Faraday’s Laws

Concept Summary

• An electrolytic cell is a type of electrochemical cell that uses an external power source to drive a chemical reaction, resulting in the decomposition of a substance.
• Electrolysis is the process of using an electrolytic cell to drive a chemical reaction, often resulting in the formation of new substances.
• Faraday's Laws describe the relationship between the amount of substance deposited or dissolved during electrolysis and the amount of electric charge passed through the cell.
• The first law states that the mass of a substance deposited or dissolved during electrolysis is directly proportional to the amount of electric charge passed through the cell.
• The second law states that the mass of a substance deposited or dissolved during electrolysis is directly proportional to the molar mass of the substance and the amount of electric charge passed through the cell.

Questions

WHAT (definitional)

1. What is an electrolytic cell?
2. Answer: An electrolytic cell is a type of electrochemical cell that uses an external power source to drive a chemical reaction, resulting in the decomposition of a substance.
3. Real-world example: Electrolytic cells are used in the production of aluminum and chlorine gas.
4. Misconception cleared: An electrolytic cell is not the same as a galvanic cell, which generates electricity through a spontaneous chemical reaction.
5. What is electrolysis?
6. Answer: Electrolysis is the process of using an electrolytic cell to drive a chemical reaction, often resulting in the formation of new substances.
7. Real-world example: Electrolysis is used to split water into hydrogen and oxygen gas.
8. Misconception cleared: Electrolysis is not the same as electroplating, which involves depositing a thin layer of a substance onto a surface using an electric current.
9. What are Faraday's Laws?
10. Answer: Faraday's Laws describe the relationship between the amount of substance deposited or dissolved during electrolysis and the amount of electric charge passed through the cell.
11. Real-world example: Faraday's Laws are used to calculate the amount of substance deposited or dissolved during electrolysis in the production of aluminum and chlorine gas.
12. Misconception cleared: Faraday's Laws do not apply to galvanic cells, which generate electricity through a spontaneous chemical reaction.

WHY (causal reasoning)

1. Why is an external power source necessary for an electrolytic cell?
2. Answer: An external power source is necessary to drive the chemical reaction in an electrolytic cell, as the reaction is not spontaneous.
3. Real-world example: Without an external power source, an electrolytic cell would not be able to decompose a substance.
4. Misconception cleared: An external power source is not necessary for a galvanic cell, which generates electricity through a spontaneous chemical reaction.
5. Why is the amount of substance deposited or dissolved during electrolysis directly proportional to the amount of electric charge passed through the cell?
6. Answer: The amount of substance deposited or dissolved during electrolysis is directly proportional to the amount of electric charge passed through the cell because the electric charge drives the chemical reaction.
7. Real-world example: The amount of aluminum deposited during electrolysis is directly proportional to the amount of electric charge passed through the cell.
8. Misconception cleared: The amount of substance deposited or dissolved during electrolysis is not directly proportional to the voltage applied to the cell.
9. Why is the molar mass of a substance important in determining the amount of substance deposited or dissolved during electrolysis?
10. Answer: The molar mass of a substance is important in determining the amount of substance deposited or dissolved during electrolysis because it affects the amount of electric charge required to drive the chemical reaction.
11. Real-world example: The molar mass of aluminum affects the amount of electric charge required to deposit a certain amount of aluminum during electrolysis.
12. Misconception cleared: The molar mass of a substance is not important in determining the voltage required to drive the chemical reaction.

HOW (process/application)

1. How is an electrolytic cell constructed?
2. Answer: An electrolytic cell consists of two electrodes (an anode and a cathode) and an electrolyte solution.
3. Real-world example: An electrolytic cell is constructed by placing the electrodes in the electrolyte solution and connecting them to a power source.
4. Misconception cleared: An electrolytic cell is not constructed by simply placing two electrodes in a solution and applying a voltage.
5. How is the amount of substance deposited or dissolved during electrolysis calculated?
6. Answer: The amount of substance deposited or dissolved during electrolysis is calculated using Faraday's Laws, which describe the relationship between the amount of substance deposited or dissolved and the amount of electric charge passed through the cell.
7. Real-world example: The amount of aluminum deposited during electrolysis is calculated using Faraday's Laws.
8. Misconception cleared: The amount of substance deposited or dissolved during electrolysis is not calculated by simply measuring the voltage applied to the cell.
9. How is electrolysis used in industry?
10. Answer: Electrolysis is used in industry to produce a variety of substances, including aluminum, chlorine gas, and hydrogen gas.
11. Real-world example: Electrolysis is used to produce aluminum in the production of aluminum foil and other aluminum products.
12. Misconception cleared: Electrolysis is not used to produce substances that are not stable under the conditions of the electrolytic cell.

CAN (possibility/conditions)

1. Can any substance be electrolyzed?
2. Answer: No, not all substances can be electrolyzed, as they may not be stable under the conditions of the electrolytic cell.
3. Real-world example: Water cannot be electrolyzed at room temperature, as it requires high temperatures and pressures to decompose.
4. Misconception cleared: Any substance can be electrolyzed if it is stable under the conditions of the electrolytic cell.
5. Can the amount of substance deposited or dissolved during electrolysis be increased by increasing the voltage applied to the cell?
6. Answer: No, the amount of substance deposited or dissolved during electrolysis is not directly proportional to the voltage applied to the cell.
7. Real-world example: Increasing the voltage applied to the cell may not increase the amount of substance deposited or dissolved during electrolysis.
8. Misconception cleared: Increasing the voltage applied to the cell may increase the rate of the chemical reaction, but it does not increase the amount of substance deposited or dissolved.
9. Can the molar mass of a substance affect the amount of substance deposited or dissolved during electrolysis?
10. Answer: Yes, the molar mass of a substance affects the amount of substance deposited or dissolved during electrolysis, as it affects the amount of electric charge required to drive the chemical reaction.
11. Real-world example: The molar mass of aluminum affects the amount of electric charge required to deposit a certain amount of aluminum during electrolysis.
12. Misconception cleared: The molar mass of a substance does not affect the voltage required to drive the chemical reaction.

TRUE/FALSE (misconception testing)

1. Statement: An electrolytic cell is a type of galvanic cell.
2. Answer: FALSE
3. Real-world example: An electrolytic cell is used to decompose a substance, whereas a galvanic cell generates electricity through a spontaneous chemical reaction.
4. Misconception cleared: An electrolytic cell is not the same as a galvanic cell.
5. Statement: The amount of substance deposited or dissolved during electrolysis is directly proportional to the voltage applied to the cell.
6. Answer: FALSE
7. Real-world example: The amount of substance deposited or dissolved during electrolysis is directly proportional to the amount of electric charge passed through the cell, not the voltage applied.
8. Misconception cleared: The amount of substance deposited or dissolved during electrolysis is not directly proportional to the voltage applied to the cell.
9. Statement: Any substance can be electrolyzed at room temperature.
10. Answer: FALSE
11. Real-world example: Water cannot be electrolyzed at room temperature, as it requires high temperatures and pressures to decompose.
12. Misconception cleared: Not all substances can be electrolyzed at room temperature, as they may not be stable under the conditions of the electrolytic cell.