Primary & Secondary Batteries
1. Which of the following is a primary battery?
a) Lead-acid battery
b) Mercury cell
c) Nickel-cadmium battery
d) Fuel cell
2. Primary batteries are
a) Rechargeable
b) Non-rechargeable
c) Used in vehicles
d) Made of lithium only
3. Give one example of a primary battery.
4. Why are secondary batteries also called storage batteries?
5. State one key difference between a primary and a secondary battery.
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Lead Storage Battery
6. What is the electrolyte used in a lead storage battery?
a) HCl
b) NaOH
c) H₂SO₄
d) NH₄OH
7. Write the overall cell reaction for a fully charged lead storage battery.
8. Which electrode acts as the cathode in a lead storage battery during discharge?
9. What happens to the density of H₂SO₄ during the discharge of a lead storage battery?
10. How many volts does a single lead-acid cell produce approximately?
a) 2 V
b) 1.5 V
c) 3.7 V
d) 9 V
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Mercury Cell
11. What is the anode in a mercury cell?
a) Zn-Hg amalgam
b) PbO₂
c) Graphite
d) Ni
12. Why does the mercury cell provide a constant voltage during its lifetime?
13. Mention one major drawback of mercury cells.
14. What is the electrolyte used in a mercury cell?
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Nickel-Cadmium (Ni-Cd) Battery
15. In a Ni-Cd battery, cadmium acts as:
a) Electrolyte
b) Anode
c) Cathode
d) Separator
16. Write the reaction at the cathode during the discharge of a Ni-Cd battery.
17. State one advantage and one disadvantage of a Ni-Cd battery.
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Fuel Cell
18. A hydrogen-oxygen fuel cell uses which gas at the anode?
a) O₂
b) N₂
c) H₂
d) CO₂
19. Write the overall cell reaction for a hydrogen-oxygen fuel cell.
20. Why are fuel cells considered en
vironmentally friendly?
Answers
Primary & Secondary Batteries
1. Which of the following is a primary battery?
Answer: b) Mercury cell
2. Primary batteries are
Answer: b) Non-rechargeable
3. Give one example of a primary battery.
Answer: Dry cell (Leclanché cell)
4. Why are secondary batteries also called storage batteries?
Answer: Because they can be recharged by passing an electric current, storing energy for future use.
5. State one key difference between a primary and a secondary battery.
Answer: Primary batteries cannot be recharged, whereas secondary batteries can be recharged and reused.
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Lead Storage Battery
6. What is the electrolyte used in a lead storage battery?
Answer: c) H₂SO₄
7. Write the overall cell reaction for a fully charged lead storage battery.
Answer:
Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(l)
8. Which electrode acts as the cathode in a lead storage battery during discharge?
Answer: Lead dioxide (PbO₂)
9. What happens to the density of H₂SO₄ during the discharge of a lead storage battery?
Answer: It decreases as H₂SO₄ gets consumed to form PbSO₄ and water.
10. How many volts does a single lead-acid cell produce approximately?
Answer: a) 2 V
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Mercury Cell
11. What is the anode in a mercury cell?
Answer: a) Zn-Hg amalgam
12. Why does the mercury cell provide a constant voltage during its lifetime?
Answer: Because the overall reaction does not involve any ions in solution phase, so concentration remains constant.
13. Mention one major drawback of mercury cells.
Answer: Mercury is toxic and poses environmental hazards.
14. What is the electrolyte used in a mercury cell?
Answer: A paste of KOH and ZnO
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Nickel-Cadmium (Ni-Cd) Battery
15. In a Ni-Cd battery, cadmium acts as:
Answer: b) Anode
16. Write the reaction at the cathode during the discharge of a Ni-Cd battery.
Answer:
2NiO(OH) + 2H₂O + 2e⁻ → 2Ni(OH)₂ + 2OH⁻
17. State one advantage and one disadvantage of a Ni-Cd battery.
Answer:
Advantage: Rechargeable and long life
Disadvantage: Cadmium is toxic and disposal is harmful to the environment
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Fuel Cell
18. A hydrogen-oxygen fuel cell uses which gas at the anode?
Answer: c) H₂
19. Write the overall cell reaction for a hydrogen-oxygen fuel cell.
Answer:
2H₂(g) + O₂(g) → 2H₂O(l)
20. Why are fuel cells considered environmentally friendly?
Answer: Because they produce only water as a by-product and do not emit harmful gases
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