Separate Chemistry: evaluate a continuously supplied fuel cell
Введено| English | Значение |
|---|---|
| fuel cell/ˈfjuːəl sel/ | топливный элемент |
| lifecycle boundary/ˈlaɪfsaɪkl ˈbaʊndəri/ | границы жизненного цикла |
What would explain this observation?
- A hydrogen fuel cell 燃料电池 continues operating while hydrogen and oxygen are supplied from outside. Its local water product does not by itself show how the hydrogen was produced.
Build the model
- Fuel cells receive fuel such as hydrogen and oxygen or air from an external source.
- The fuel is oxidised electrochemically, producing a potential difference.
- In a hydrogen fuel cell the overall reaction is 2H₂ + O₂ → 2H₂O.
- This transfers chemical energy electrically to a circuit rather than requiring the fuel to burn in a flame.
- External fuel supply distinguishes it from a rechargeable battery containing its stored reactants.
- fuel cell: A cell producing electricity from electrochemical reactions with externally supplied fuel and oxidant.
- lifecycle boundary 生命周期边界: The stated production, use and disposal stages included in an evaluation.
Which claim follows directly from 2H₂ + O₂ → 2H₂O?
Сложность 1/5 · 100 монет + небольшой бонус за первое выполнение сегодня
The equation 2H2 + O2 -> 2H2O states the local product: water. It says nothing about how the hydrogen was manufactured, and a fuel cell needs continuous fuel - that is what distinguishes it from a battery.
Match each technical term to its precise meaning.
Сложность 2/5 · 140 монет + небольшой бонус за первое выполнение сегодня
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Compare both devices against a purpose.
- Supplied information may include mass, operating time, refuelling or charging time, infrastructure, fuel storage and cost.
- Water is the direct product of the hydrogen–oxygen reaction; hydrogen production and transport may have other environmental effects.
- A conclusion about total emissions needs data for those stages.
- Do not infer zero lifecycle carbon emissions merely from the absence of carbon in the local equation.
In the lab: Use a teacher-approved educational fuel-cell kit or supplied observations; never improvise compressed hydrogen storage or a hydrogen–oxygen gas mixture. Record how fuel is supplied, where the electrical circuit connects and what product forms. A comparison task must use the given boundary: device-only, fuel production or a wider lifecycle. Detailed commercial engineering is not required, and the electron half equations are in the separate Higher lesson.
Which two habits make the investigation or model in this case more defensible?
Сложность 2/5 · 140 монет + небольшой бонус за первое выполнение сегодня
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a supplied model device runs 4 hours per fuel cartridge; a rechargeable device runs 3 hours per full charge.
- Twelve uninterrupted hours require three cartridges or four battery charge-equivalents, ignoring the stated changeover time.
- This is an operating-time comparison, not proof of lower cost or environmental impact.
- In the balanced chemical equation, six represented H₂ molecules need three O₂ and form six H₂O molecules.
Your turn: In 2H₂ + O₂ → 2H₂O, how many O₂ molecules react with ten represented H₂ molecules?
In 2H₂ + O₂ → 2H₂O, how many O₂ molecules react with ten represented H₂ molecules?
Сложность 2/5 · 140 монет + небольшой бонус за первое выполнение сегодня
The result is 5 molecules. Known: 2H2 + O2 -> 2H2O, so 2 H2 molecules react with 1 O2. For ten H2 molecules: 10/2 = 5 O2 molecules. The coefficient ratio carries the count.
Check the conclusion and its limits
- A fuel cell does not manufacture its own limitless hydrogen, and oxygen is a reactant, not its waste product.
- A rechargeable battery requires charging energy while the fuel cell needs a continuing external fuel supply.
- Neither device is automatically the best under every combination of cost, storage and environmental conditions.
Not true: A water-only local product proves zero environmental impact over the whole lifecycle. The water-only product holds at the CELL. Making the hydrogen - by electrolysis or from natural gas - and building the equipment carry their own emissions, so the lifecycle impact is never zero by default.
- Fuel cells receive fuel such as hydrogen and oxygen or air from an external source.
- Compare both devices against a purpose.
- Watch for: A fuel cell does not manufacture its own limitless hydrogen, and oxygen is a reactant, not its waste product.
The water-only product holds at the CELL.
Сложность 1/5 · 100 монет + небольшой бонус за первое выполнение сегодня
True. The water-only product holds at the CELL. Making the hydrogen - by electrolysis or from natural gas - and building the equipment carry their own emissions, so the lifecycle impact is never zero by default.
A cell producing electricity from electrochemical reactions with externally supplied fuel and oxidant: write the technical term.
Сложность 1/5 · 100 монет + небольшой бонус за первое выполнение сегодня
fuel cell means A cell producing electricity from electrochemical reactions with externally supplied fuel and oxidant.