Batteries Primary and Secondary Lead Storage Fuel Cell - UNSOLVED PRACTICE SET
Chapter: Electrochemistry | Topic: Batteries Primary and Secondary Lead Storage Fuel Cell
BATTERIES PRIMARY AND SECONDARY LEAD STORAGE FUEL CELL - UNSOLVED PRACTICE SET
Topic: Batteries Primary and Secondary Lead Storage Fuel Cell
Multiple Choice Questions
Q1. In a lead storage battery, the electrolyte used is:
- Dilute HCl
- Dilute H₂SO₄
- Dilute HNO₃
- NaOH solution
Q2. A dry cell (Leclanché cell) used in torches and TV remotes is an example of a:
- Secondary battery
- Fuel cell
- Primary battery
- Concentration cell
Q3. In a H₂–O₂ fuel cell, the reaction at the cathode is:
- H₂ + 2OH⁻ → 2H₂O + 2e⁻
- O₂ + 2H₂O + 4e⁻ → 4OH⁻
- 2H₂ + O₂ → 2H₂O
- H₂ → 2H⁺ + 2e⁻
Q4. During the discharge of a lead storage battery, the substance that gets reduced at the cathode is:
- Pb
- PbO₂
- PbSO₄
- H₂SO₄
Q5. Which of the following is a secondary battery?
- Dry cell (Leclanché cell)
- Mercury cell
- Nickel-cadmium (Ni-Cd) cell
- Zinc-carbon cell
Q6. The main advantage of a fuel cell over a conventional battery is:
- It is cheaper to manufacture
- It produces water as the only by-product and can be recharged by refuelling
- It has a higher voltage output
- It does not require any catalyst
Short Answer Questions
Q7. Differentiate between a primary battery and a secondary battery. Give one example of each that you use in your daily life. (Hint: Think about the battery in your TV remote versus the one in your smartphone!)
Q8. Write the anode and cathode reactions during the discharge of a lead storage battery. What happens to the density of the electrolyte during discharge?
Q9. What is a fuel cell? Name the two gases used in a H₂–O₂ fuel cell. What is the only product formed in this fuel cell?
Q10. Explain why the voltage of a dry cell (Leclanché cell) drops after prolonged use. What chemical change occurs at the anode that causes this?
Q11. During the charging of a lead storage battery, what happens at the anode and cathode? Write the reactions and explain how PbSO₄ is converted back to Pb and PbO₂.
Q12. Why are fuel cells considered more environmentally friendly than conventional fossil fuel-based power plants? Give two reasons.
Long Answer Questions
Q13. (a) Describe the construction and working of a dry cell (Leclanché cell). Draw a neat labelled diagram showing the anode, cathode, electrolyte, and other components.
(b) Write the reactions occurring at the anode and cathode.
(c) Why is a dry cell called "dry" even though it contains a moist paste?
Q14. (a) Describe the construction and working of a lead storage battery. Draw a neat labelled diagram.
(b) Write the reactions occurring at the anode and cathode during both discharge and charging processes.
(c) Why is the density of the electrolyte (dilute H₂SO₄) checked regularly in automobile workshops? What does a decrease in density indicate?
Q15. (a) What is a fuel cell? Describe the construction and working of a H₂–O₂ fuel cell with a labelled diagram.
(b) Write the reactions occurring at the anode and cathode in acidic and alkaline medium.
(c) Why are fuel cells considered ideal for use in space vehicles and electric vehicles? Give two reasons.
Numerical / Application-Based Problems
Q16. A lead storage battery has an emf of 2.0 V per cell. A car battery consists of 6 such cells connected in series.
(a) What is the total emf of the car battery?
(b) During discharge, the overall reaction is: Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O
Calculate the mass of H₂SO₄ consumed when the battery delivers 1 mole of electrons.
(c) If the density of H₂SO₄ in a fully charged battery is 1.28 g mL⁻¹ and it drops to 1.15 g mL⁻¹ when discharged, explain what this change indicates about the state of charge of the battery.
(Given: Atomic masses: H = 1, S = 32, O = 16, Pb = 207 u)
Q17. A H₂–O₂ fuel cell operates at 25°C and 1 atm pressure. The standard electrode potentials are: E°(O₂/H₂O) = +1.23 V and E°(H⁺/H₂) = 0.00 V.
(a) Write the half-cell reactions at the anode and cathode.
(b) Calculate the standard emf of the fuel cell.
(c) If the fuel cell produces 1.8 kg of water per hour, calculate the mass of hydrogen gas consumed per hour.
(d) Why is this fuel cell considered environmentally friendly compared to a petrol engine in a car?
(Given: Atomic masses: H = 1, O = 16 u)
Q18. An electric vehicle (EV) company in India is testing a new battery system for their cars. They compare a lead-acid battery with a nickel-metal hydride (Ni-MH) battery.
(a) Classify each battery as primary or secondary. Justify your answer.
(b) The lead-acid battery has an energy density of about 30–50 Wh/kg, while the Ni-MH battery has an energy density of about 60–120 Wh/kg. What does "energy density" mean, and why is a higher energy density important for electric vehicles?
(c) Write the discharge reactions for a Ni-MH battery, given that the anode reaction is: MH + OH⁻ → M + H₂O + e⁻ (where M is a metal alloy) and the cathode reaction involves NiO(OH) being reduced to Ni(OH)₂.
(d) Why are electric vehicles with zero tailpipe emissions becoming increasingly popular in Indian cities like Delhi and Bengaluru? Give two environmental reasons.