AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to: evaluate the use of hydrogen fuel cells in…
Full specification wording
Fuel cells: Students should be able to: evaluate the use of hydrogen fuel cells in comparison with rechargeable cells and batteries (HT only) write the half equations for the electrode reactions in the hydrogen fuel cell. AQA GCSE Chemistry 8462. GCSE exams Jun
Evaluating hydrogen fuel cells means weighing advantages, such as continuous electricity while hydrogen and oxygen are supplied and water as the only chemical product, against drawbacks, such as…
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 5 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Evaluating hydrogen fuel cells means weighing advantages, such as continuous electricity while hydrogen and oxygen are supplied and water as the only chemical product, against drawbacks, such as the energy and cost of producing, storing and transporting hydrogen. Rechargeable cells and batteries store reactants internally and must be recharged, but they are familiar and widely available. Balancing atoms and charges is essential for these HT equations.
What earns the marks
- An evaluation should include both advantages and disadvantages of hydrogen fuel cells compared with rechargeable cells and batteries, not just one side.
- A valid advantage is that a fuel cell produces electricity continuously while reactants are supplied and its only chemical product is water.
- A valid drawback is that hydrogen must be produced, stored and transported, which can use energy and may involve fossil fuels.
- (HT only) The anode half equation for hydrogen oxidation in acidic conditions is H₂ → 2H⁺ + 2e⁻.
- (HT only) The cathode half equation for oxygen reduction in acidic conditions is O₂ + 4H⁺ + 4e⁻ → 2H₂O.
- (HT only) Half equations must balance both atoms and charge, and the electrons lost at the anode must equal the electrons gained at the cathode when the equations are combined.
Common mistakes and how to put them right
Giving only advantages or only disadvantages in an evaluation.
Put it right by including both and reaching a supported judgement.
(HT only) Writing a half equation that balances atoms but not charge.
Put it right by checking that the total charge is the same on both sides.
(HT only) Putting the oxidation half equation at the cathode.
Put it right by placing hydrogen oxidation at the anode and oxygen reduction at the cathode.
(HT only) Mixing acidic and alkaline half-equations for the same fuel cell.
Put it right by using consistent conditions (e.g., both acidic).
Exam tips
- For evaluation questions, structure your answer as advantages, disadvantages and a short overall judgement.
- (HT only) When writing half equations, balance atoms first and then add electrons to balance charge.
- (HT only) Check that the number of electrons lost at the anode equals the number gained at the cathode before combining the half equations.
Try the lesson
The start of the Fuel cells: Students should be able to: evaluate the use of hydrogen fuel cells in comparison with rechargeable cells and batteries (HT only) write the half equations for the electrode reactions in the hydrogen fuel cell. AQA GCSE Chemistry 8462. GCSE exams Jun lesson, made from checked teaching notes for this specification point.
Have a go first
Which of the following is an advantage of using hydrogen fuel cells rather than rechargeable batteries to power electric vehicles?
Listen
Evaluating hydrogen fuel cells means weighing advantages, such as continuous electricity while hydrogen and oxygen are supplied and water as the only chemical product, against drawbacks, such as the energy and cost of producing, storing and transporting hydrogen. Rechargeable cells and batteries store reactants internally and must be recharged, but they are familiar and widely available. Balancing atoms and charges is essential for these HT equations. A strong answer earns marks for these points. An evaluation should include both advantages and disadvantages of hydrogen fuel cells compared with rechargeable cells and batteries, not just one side. A valid advantage is that a fuel cell produces electricity continuously while reactants are supplied and its only chemical product is water. A valid drawback is that hydrogen must be produced, stored and transported, which can use energy and may involve fossil fuels. HT only) The anode half equation for hydrogen oxidation in acidic conditions is H₂ → 2H⁺ + 2e⁻. A common slip: Giving only advantages or only disadvantages in an evaluation. Instead, including both and reaching a supported judgement. Exam tip: For evaluation questions, structure your answer as advantages, disadvantages and a short overall judgement.
See it
Key words
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Evaluating hydrogen fuel cells
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Rechargeable cells and batteries
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Half equations
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Anode
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See every definition
- Evaluating hydrogen fuel cells
- Weighing advantages, such as continuous electricity while hydrogen and oxygen are supplied and water as the only chemical product, against drawbacks, such as the energy and cost of producing, storing and transporting hydrogen.
- Rechargeable cells and batteries
- These store reactants internally and must be recharged, but they are familiar and widely available.
- Half equations
- These show what happens at each electrode, and balancing atoms and charges is essential for them.
- Anode
- In acidic conditions, hydrogen is oxidised here to hydrogen ions and electrons.
Label the diagram
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Test your understanding of Fuel cells: Students should be able to: evaluate the use of hydrogen fuel cells in comparison with rechargeable cells and batteries (HT only) write the half equations for the electrode reactions in the hydrogen fuel cell. AQA GCSE Chemistry 8462. GCSE exams Jun
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