Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

5.1.6Unit 5. Transition Metals and Organic Nitrogen Chemistry

Fuel Cells — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions

5 min read 5 parts Lesson 12 of 43 Unit quiz

📚 IAL Edexcel Linear (Chemistry) Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read

Part 1 of 5How a Fuel Cell Works

5.1.6 Fuel Cells
Continuous supply
  • Hydrogen and oxygen are fed in continuously, so the cell keeps producing electricity as long as the fuel is supplied.
Electrodes
  • Porous electrodes carrying a platinum catalyst let gas, electrolyte and catalyst meet at one surface.
Anode
  • Hydrogen is oxidised at the negative electrode, releasing electrons that travel through the external circuit.
Cathode
  • Oxygen is reduced at the positive electrode, where it gains the electrons from the external circuit.
Product
  • The only chemical product of the hydrogen-oxygen cell is water.

Part 2 of 5Electrode Reactions

Electrode Reactions
Acidic anode
  • H₂ → 2H⁺ + 2e⁻, with E⦵ = 0.00 V for the reverse reduction.
Acidic cathode
  • O₂ + 4H⁺ + 4e⁻ → 2H₂O, with E⦵ = +1.23 V.
Alkaline anode
  • H₂ + 2OH⁻ → 2H₂O + 2e⁻, with E⦵ = -0.83 V for the reverse reduction.
Alkaline cathode
  • O₂ + 2H₂O + 4e⁻ → 4OH⁻, with E⦵ = +0.40 V, giving the same overall cell voltage of +1.23 V.

Part 3 of 5Evaluation

Evaluation
Efficiency
  • Fuel cells convert chemical energy directly to electrical energy and are more efficient than burning fuel in an engine.
Pollution
  • No carbon dioxide is released at the point of use, though making the hydrogen may require energy from fossil fuels.
Storage
  • Hydrogen is difficult to store and transport because it is a gas of very low density and is flammable.
Cost
  • Platinum catalysts are expensive, and the cells need a reliable fuel supply and infrastructure.
FeatureFuel cellRechargeable cell
ReactantsSupplied continuouslyContained in the cell
RechargingNot needed, just refuelNeeds an external supply of electricity

Part 4 of 5Worked Example

Question

  • Calculate the free energy released when 1 mol of hydrogen is used in a cell with E⦵cell = +1.23 V.
  • Use F = 96 500 C mol⁻¹.

  1. Each mole of H₂ gives 2 mol of electrons, so n = 2.
  2. ΔG⦵ = -nFE⦵cell = -2 x 96 500 x 1.23 = -237 390 J.
  3. This is -237 kJ mol⁻¹ to 3 s.f.

Answer About 237 kJ is available per mole of hydrogen

Part 5 of 5Exam Checklist & Tips

5.1.6 – Key Points for the Exam

  • Fuel cell A cell that generates electricity from fuel supplied continuously.
  • Anode Electrode where oxidation occurs.
  • Electrolyte Ion-conducting medium, acid or alkali, completing the circuit.
  • Catalyst Platinum that speeds up the electrode reactions.

Common Mistakes

  • Saying that fuel cells burn the hydrogen in a flame.
  • Writing the overall equation with different amounts of H₂ and O₂ than 2 : 1.
  • Claiming a fuel cell has zero environmental impact when hydrogen production is ignored.
  • Mixing up which electrode is positive and which is negative.

Last updated:

Cambridge 9700 AS Biology Core Formula

Magnification Triangle & Unit Conversion

Formula: M = I / A  ⇔  A = I / M  ⇔  I = M × A

Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.