9.3.2Metals
Hydrogen Fuel Cells — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 4 parts Lesson 8 of 8 Unit quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 4How a Hydrogen Fuel Cell Works
A fuel cell produces electricity from a fuel reacting with oxygen, without burning it.
1
A hydrogen-oxygen fuel cell generates electricity from the reaction of hydrogen with oxygen.
2
Hydrogen is oxidised at the negative electrode, and oxygen is reduced at the positive electrode.
3
The overall reaction is 2H₂ + O₂ → 2H₂O, and it is exothermic.
4
Electrons travel through the external circuit from the hydrogen electrode to the oxygen electrode, providing the electric current.
Section 2 of 4Advantages and Disadvantages
Hydrogen is a promising fuel, but its production and storage have drawbacks.
Renewable
- Renewable Hydrogen can be made from water, so the fuel supply is renewable when the electricity used is renewable.
Clean product
- Clean product Burning hydrogen gives only water, so it does not add carbon dioxide or acid-forming gases to the air.
Production
- Production Making hydrogen by electrolysis of water needs large amounts of electricity.
Storage and safety
- Storage and safety Hydrogen must be stored in bulky pressurised containers, and it forms an explosive mixture with air.
Section 3 of 4Equations and Uses
Both word and symbol equations must be known for the fuel cell reaction.
Equations and Uses
Word equation
- Word equation Hydrogen + oxygen → water is the word equation for the overall fuel cell reaction.
Symbol equation
- Symbol equation 2H₂ + O₂ → 2H₂O, with four hydrogen atoms and two oxygen atoms on each side.
Uses
- Uses Hydrogen fuel cells are used to power spacecraft and some cars.
Energy
- Energy The reaction releases energy as electricity and heat, which is why the overall reaction is exothermic.
Section 4 of 4Exam Checklist & Tips
9.3.2 – Key Points for the Exam
- Fuel cell A device that converts the chemical energy of a fuel and oxygen directly into electrical energy.
- Electrolysis The use of electricity to break down a compound, such as water, into elements.
- Renewable energy source A source that is replaced naturally and does not run out.
- Explosive mixture A mixture, such as hydrogen and air, that can ignite and explode.
Common Mistakes
- Writing the fuel cell equation without balancing it, such as H₂ + O₂ → H₂O.
- Saying that a hydrogen fuel cell produces carbon dioxide; its only product is water.
- Claiming hydrogen is always renewable;
- it is only renewable when the electricity used to make it comes from renewable sources.
- Forgetting that the fuel cell reaction is exothermic when describing its energy change.
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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.