A small electric vehicle is powered by rechargeable lead-acid car batteries. The energy that drives the vehicle comes from the cell reaction Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l) The equation for the anode half reaction is Pb(s) + H2SO4(aq) → PbSO4(s) + 2H+(aq) + 2e-. a. Write the equation for the cathode half reaction. b. In this vehicle, each battery operates at 12.0 V. When fully charged, the vehicle can travel on a level surface for 2.5 hours with an average energy consumption of 1.0 kJ s-1, after which time the batteries must be recharged. i. How much energy, in kJ, is used by the vehicle in travelling for 2.5 hours? ii. Write the equation for the overall chemical reaction that occurs when the battery is being recharged. iii. What voltage should be used to recharge each battery?

SSCE VCE Chemistry Primary Galvanic Cells and Fuel Cells as Sources of Energy: A small electric vehicle is powe

A small electric vehicle is powered by rechargeable lead-acid car batteries - VCE - SSCE Chemistry - Question 4 - 2004 - Paper 1

Question 4

A small electric vehicle is powered by rechargeable lead-acid car batteries. The energy that drives the vehicle comes from the cell reaction Pb(s) + PbO2(s) + 2H2SO... show full transcript

Worked Solution & Example Answer:A small electric vehicle is powered by rechargeable lead-acid car batteries - VCE - SSCE Chemistry - Question 4 - 2004 - Paper 1

Step 1

Write the equation for the cathode half reaction.

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Answer

The cathode half-reaction involves the reduction of lead dioxide (PbO2) in the presence of sulfuric acid (H2SO4). The balanced equation for the cathode half reaction is:

$PbO_2(s) + 2H^+(aq) + 2e^- → PbSO_4(s) + H_2O(l)$

Step 2

How much energy, in kJ, is used by the vehicle in travelling for 2.5 hours?

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Answer

To calculate the energy consumed while travelling, we first convert the travel time into seconds:

$2.5 ext{ hours} = 2.5 imes 3600 = 9000 ext{ seconds}$

With an average energy consumption of 1.0 kJ/s, the total energy used is:

$ext{Energy} = ext{Power} imes ext{Time} = 1.0 ext{ kJ/s} imes 9000 ext{ s} = 9000 ext{ kJ}$

Step 3

Write the equation for the overall chemical reaction that occurs when the battery is being recharged.

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Answer

The overall reaction for recharging the battery involves reversing the initial reaction. The equation is:

$2PbSO_4(s) + 2H_2O(l) → Pb(s) + PbO_2(s) + 2H_2SO_4(aq)$

Step 4

What voltage should be used to recharge each battery?

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The voltage required to recharge the batteries must be higher than the nominal voltage of 12 V. Therefore, a suitable recharging voltage would be:

$ext{Recharging voltage} > 12 ext{ V}$

Typically, a voltage of at least 13.8 V is often used to ensure proper charging.

A small electric vehicle is powered by rechargeable lead-acid car batteries - VCE - SSCE Chemistry - Question 4 - 2004 - Paper 1

Worked Solution & Example Answer:A small electric vehicle is powered by rechargeable lead-acid car batteries - VCE - SSCE Chemistry - Question 4 - 2004 - Paper 1

Write the equation for the cathode half reaction.

How much energy, in kJ, is used by the vehicle in travelling for 2.5 hours?

Write the equation for the overall chemical reaction that occurs when the battery is being recharged.

What voltage should be used to recharge each battery?

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