Fuel Cells
Master Fuel Cells for GCSE Chemistry with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. A separate (triple) chemistry topic: a hydrogen fuel cell produces electricity with only water as the product, 2H₂ + O₂ → 2H₂O.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
A fuel cell is supplied with a fuel and oxygen, and uses the energy from the reaction between them to produce electrical energy efficiently. This is a Triple-only topic.
The hydrogen fuel cell is the required example. The overall reaction is hydrogen + oxygen → water, and it is an oxidation of hydrogen. Unlike a battery, a fuel cell does not run down or need recharging, because fuel is supplied continuously.
The advantages are that the only waste product is water, so there is no pollution at the point of use, and there are no moving parts to wear out. The disadvantages are that hydrogen is a gas that is difficult to store safely, and producing the hydrogen in the first place often requires energy from fossil fuels.
Revision notes
How fuel cells work
A fuel and oxygen are supplied continuously to the cell.
The fuel is oxidised electrochemically, and the energy from the reaction produces a potential difference. Because fuel is supplied continuously, the cell does not run down or need recharging.
The hydrogen fuel cell
The overall reaction is hydrogen + oxygen → water.
The hydrogen is oxidised. The only product is water, so there is no pollution at the point of use — no carbon dioxide and no other exhaust gases.
Evaluation
Advantages: only water is produced, there are no moving parts to wear out, and they do not need recharging.
Disadvantages: hydrogen is a gas that is difficult to store safely, it is highly flammable, and producing hydrogen usually requires energy which may come from fossil fuels.
Key points
- A fuel cell is supplied with fuel and oxygen.
- The fuel is oxidised to produce electrical energy.
- Hydrogen + oxygen → water is the required example.
- Fuel cells do not run down or need recharging.
- The only waste product is water.
- Hydrogen is difficult to store safely.
Worked examples
Example 1
Write the overall equation for the hydrogen fuel cell reaction. [2 marks]
Model answer
Hydrogen + oxygen → water. Correct reactants (1 mark). Correct product (1 mark).
Example 2
Give two advantages of hydrogen fuel cells over rechargeable batteries. [2 marks]
Model answer
They do not need to be recharged, because fuel is supplied continuously (1 mark). The only waste product is water, so there is no pollution at the point of use (1 mark).
Example 3
Give two disadvantages of using hydrogen fuel cells in cars. [2 marks]
Model answer
Hydrogen is a gas that is difficult to store safely and is highly flammable (1 mark). Producing the hydrogen requires energy, which often comes from burning fossil fuels (1 mark).
Common mistakes
Saying fuel cells produce no pollution at all.
There is none at the point of use, but producing the hydrogen may cause pollution.
Saying fuel cells need recharging.
They do not, because fuel is supplied continuously.
Giving carbon dioxide as a product.
The only product of a hydrogen fuel cell is water.
Giving only advantages.
Evaluation questions require disadvantages too.
Exam tips
- Learn the overall equation and that hydrogen is oxidised.
- Say no pollution at the point of use rather than no pollution.
- Give both advantages and disadvantages when evaluating.
- Remember this is a Triple-only topic.
Key terms
- Fuel cell
- A cell producing electricity from a continuously supplied fuel.
- Oxidation
- The loss of electrons, occurring to the hydrogen fuel.
- Point of use
- Where the cell is operating, as distinct from where fuel is made.
- Potential difference
- The voltage produced by the cell.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.