Questions about Electrolysis of Molten Salts
Electrolysis of Molten Salts – Multiple Choice Questions
Questions
1. What is the main characteristic of molten salts that allows electrolysis to occur?
A) They are solid at room temperature
B) They conduct electricity when molten
C) They have high vapor pressure
D) They react violently with water
E) They emit light when heated
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2. During the electrolysis of molten NaCl, which ion migrates to the cathode?
A) Cl⁻
B) Na⁺
C) H⁺
D) OH⁻
E) O²⁻
3. What product forms at the cathode during the electrolysis of molten NaCl?
A) Cl₂ gas
B) Na metal
C) H₂ gas
D) NaCl solid
E) O₂ gas
4. At the anode in molten salt electrolysis, which process occurs?
A) Reduction
B) Oxidation
C) Neutralization
D) Hydrolysis
E) Precipitation
5. Which product is formed at the anode during the electrolysis of molten NaCl?
A) Cl₂ gas
B) Na metal
C) H₂ gas
D) O₂ gas
E) Na⁺ ions
6. Why can molten salts conduct electricity?
A) They have free electrons
B) Ions are free to move in the liquid state
C) They contain dissolved gases
D) They are acidic
E) They have a high boiling point
7. In the electrolysis of molten Al₂O₃, which product forms at the cathode?
A) Oxygen gas
B) Aluminum metal
C) Aluminum oxide
D) Hydrogen gas
E) Carbon dioxide
8. During the electrolysis of molten Al₂O₃, what forms at the anode?
A) Oxygen gas
B) Aluminum metal
C) Carbon monoxide
D) Water
E) Chlorine gas
9. What is the role of carbon electrodes in the electrolysis of molten aluminum oxide?
A) React with aluminum
B) Serve as inert electrodes
C) React with oxygen to form CO and CO₂
D) Reduce alumina to aluminum ions
E) Catalyze the reaction
10. Why is Al₂O₃ mixed with cryolite for electrolysis?
A) To increase melting point
B) To lower melting point and improve conductivity
C) To produce more oxygen
D) To reduce aluminum ions
E) To form solid electrolytes
11. What happens to the positive ions in molten salt during electrolysis?
A) They migrate to the anode
B) They migrate to the cathode
C) They stay in the middle
D) They convert to neutral atoms in solution
E) They evaporate
12. Which of the following is a necessary condition for electrolysis of molten salts?
A) Presence of water
B) Solid state of salt
C) Molten or liquid state to allow ion movement
D) Low temperature
E) Low voltage
13. During electrolysis of molten CaCl₂, what is produced at the cathode?
A) Ca metal
B) Cl₂ gas
C) Ca²⁺ ions
D) H₂ gas
E) O₂ gas
14. What is the main difference between electrolysis of aqueous salt solutions and molten salts?
A) Only molten salts conduct electricity
B) Molten salts only produce gases
C) Aqueous solutions have water which can participate in reactions
D) Molten salts cannot be electrolyzed
E) Aqueous solutions do not have ions
15. The anode in molten salt electrolysis is usually made of:
A) Platinum
B) Copper
C) Carbon (graphite)
D) Aluminum
E) Iron
16. Electrolysis of molten salts is an example of:
A) A spontaneous redox reaction
B) An electrolytic cell operation
C) A galvanic cell reaction
D) A combustion reaction
E) A neutralization reaction
17. Which ion is reduced at the cathode during molten salt electrolysis?
A) Anion
B) Cation
C) Neutral atom
D) Electron
E) None of these
18. What determines the products formed during molten salt electrolysis?
A) The electrolyte’s boiling point
B) The voltage applied
C) The ions present and their relative reduction/oxidation potentials
D) The color of the molten salt
E) The shape of the electrodes
19. During electrolysis, why does the electrolyte need to be molten rather than solid?
A) To increase the reaction speed
B) To allow ions to move freely and carry current
C) To increase pressure
D) To make the cell smaller
E) To produce more heat
20. What is the standard oxidation half-reaction at the anode in molten NaCl electrolysis?
A) 2Na⁺ + 2e⁻ → 2Na
B) 2Cl⁻ → Cl₂ + 2e⁻
C) Cl₂ + 2e⁻ → 2Cl⁻
D) Na → Na⁺ + e⁻
E) Na⁺ + e⁻ → Na
Answers and Explanations
1. B – Molten salts conduct electricity because their ions are free to move.
2. B – Na⁺ ions migrate to the cathode.
3. B – Na⁺ gains electrons to form Na metal at the cathode.
4. B – Oxidation occurs at the anode.
5. A – Cl⁻ ions lose electrons to form Cl₂ gas at the anode.
6. B – In molten state, ions are mobile allowing conduction.
7. B – Aluminum metal forms at the cathode.
8. A – Oxygen gas is released at the anode.
9. C – Carbon electrodes react with oxygen forming CO and CO₂.
10. B – Cryolite lowers melting point, improving conductivity and efficiency.
11. B – Positive ions (cations) move to the cathode.
12. C – The salt must be molten or liquid for ions to move.
13. A – Calcium metal forms at the cathode.
14. C – Water in aqueous solutions participates in side reactions unlike molten salts.
15. C – Carbon (graphite) is commonly used for anodes in molten salt electrolysis.
16. B – Electrolysis of molten salts is an electrolytic cell process.
17. B – Cations are reduced at the cathode.
18. C – Products depend on the ions present and their electrode potentials.
19. B – Melting allows ions to move freely, enabling current flow.
20. B – Oxidation half-reaction: 2Cl⁻ → Cl₂ + 2e⁻.
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