fuel cell: a device that converts chemical energy into electrical energy. in the hydrogen- oxygen...
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C5 FUEL CELLS AND RECHARGEABLE BATTERIES
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C.5.1 Describe how a hydrogen-oxygen fuel cell works.
Fuel cell: A device that converts chemical energy into electrical energy.
In the hydrogen-oxygen fuel cell, both cathode and anode are made of porous carbon with platinum or palladium.
The electrolyte solution used is KOH or NaOH.
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C.5.1 Describe how a hydrogen-oxygen fuel cell works.
What is the half reaction occurring at the anode?
A: 2H2(g) + 4OH- (aq) → 4H2O (I) + 4e-
What is the half reaction occurring at the cathode?
A: O2 (g) + 2H2O(I) + 4e- → 4OH- (aq) After cancelling, what is the overall
reaction? A: 2H2 (g) + O2 (g) → 2H2O (I)
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C.5.1 Describe how a hydrogen-oxygen fuel cell
works. You also need to know the half reactions
in acidic conditions: Anode: 2H2(g) → 4H+(aq) + 4e-
Cathode: O2 + 4H+ + 4e- → 2H2O
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C.5.2 Describe the workings of rechargeable batteries.
Rechargeable batteries are like voltaic cells. Except that you can add electricity to make the reaction go the other way.
Lead-acid batteries are used in cars. Sulfuric acid is the electrolyte.
The anode is made of lead plates, the cathode is made of lead(IV) oxide plates.
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C.5.2 Describe the workings of rechargeable batteries.
What is the reaction happening at the anode?
A: Pb(s)+SO42-(aq) → PbSO4(s) + 2e-
What is the reaction happening at the cathode?
PbO2(s) + 4H+(aq) + SO42-(aq) + 2e-
→ PbSO4(s) + 2H2O(l) Overall reaction? Pb(s) + PbO2(s) + H2SO4(aq) → 2PbSO4 +
2H2O
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C.5.2 Describe the workings of rechargeable batteries.
The battery is then recharged using an alternator when the car is running.
2PbSO4(s) + 2H2O(l) → Pb(s) + PbO2(s) + 2H2SO4(aq)
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C.5.2 Describe the workings of rechargeable batteries.
Nickel-cadmium batteries are used as lightweight batteries (AA, AAA, etc.)
KOH is used as an electrolyte. The reaction at the anode? Cd(s) + 2OH-(aq) → Cd(OH)2(s) + 2e- Reaction at the cathode? NiO(OH)(s) + H2O(l) + e- → Ni(OH)2(s) + OH-
(aq) Overall reaction? Cd(s) + 2NiO(OH)(s) + 2H2O(l) → Cd(OH)2(s) +
Ni(OH)2(s)
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Help your Earth!! Cadmium is an
extremely toxic heavy metal, so when disposing of rechargeable batteries, make sure you dispose of them (just like any battery) in a special drop-off for batteries.
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C.5.2 Describe the workings of rechargeable batteries.
Lithium ion batteries are used in products such as cell phones and laptops.
It typically contains a graphite anode, and a metal oxide cathode. The electrolyte is a lithium salt.
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C.5.3 Discuss the similarities and differences between fuel cells and rechargeable batteries.
SimilaritiesBoth devices convert chemical energy into
electricalBoth have redox reactions taking place at the
anodes and cathodes.
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C.5.3 Discuss the similarities and differences between fuel cells and rechargeable
batteries.Differences
Fuel cells convert energy and rechargeable batteries store energy.
Fuel cell requires a constant supply of reactants. Batteries have stored chemical energy and provide energy until they are used up.
Batteries can be recharged. A fuel cell does not need recharging, but needs a continuous supply of fuel.
The electrodes in fuel cells are made of inert materials.
Fuel cells are more expensive than batteries.