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Hydrogen/Fuel Cells
| Question | Answer |
|---|---|
| Non rechargeable/Primary | provides electrical energy until chemicals have reacted to extent that V fails |
| Rechargeable/Secondry | chemicals react recharging reaction is reversed and chemicals are regenerated |
| Examples of secondry cell | Ni/Cadmium Li ion/Li polymer (laptops) |
| Fuel Cells | external supplies fuel+oxidant continual electrical supply as long as reactants supplied |
| Which terminal in the fuel cell provides electrons? | -ve terminal (no recharging required) |
| What does a fuel cell required | electrolyte fuel/oxidants |
| Where does the hydrogen come from for hydrogen cars? | H2g/hydrogen rich fuels (methanol, natural gas, petrol) |
| How is the hydrogen generated? | Fuel reacted with water to produce hydrogen and CO2 |
| Why is methanol used as a fuel? | easier to store than a gas generated from biomass CO2 is produced |
| Advantages of Hydrogen | less CO2 less pollution/ air pollutants greater efficiency/ fuel consumption |
| How is hydrogen stored | liquid under pressure adsorbed absorbed into lattice structure |
| Limitiations | Toxic chemicals in fuel cells Fuel cells have a limited lifetime Absorbers/adsorbers limited lifespan Feasibility of storing a pressurised liquid Large scale storage and transport (cost effective/infrastructure) |
| Hydrogen economy | hydrogen must be accepted as a fuel problems with handling and maintanence engergy carrier not energy source |
| What is a battery | more than one cell joined together |
| example of primary batteries | zinc-carbon alakaline lithium |
| Examples of secondary batteries | Li ion lead-acid nickel-cadmium |
| During the reverse reaction what happens to the products from the forward reaction | products stick to electrodes not dispearsed into the electrolyte |