An emergency communications station must operate continuously for 14 days after severe weather blocks the access road.
The station requires 5.0 kWh of electrical energy each day. A technician remains at the station and can replace empty fuel containers. Each full container is connected separately.
A rechargeable chemical cell is kept at the station as a backup. It is initially fully charged, can power the station for at least 15 minutes, and can be fully recharged between successive container changes with either fuel cell.
Engineers compare a hydrogen/oxygen fuel cell with a methanol/oxygen fuel cell.
| Fuel cell | Electrical energy supplied by one full container (kWh) | Mass of one full container (kg) | Time to replace an empty container (min) | Cost of one full container (£) | Fuel storage |
|---|---|---|---|---|---|
| hydrogen/oxygen | 18 | 32 | 15 | 135 | high-pressure gas cylinder |
| methanol/oxygen | 6.0 | 5.0 | 3 | 42 | sealed liquid cartridge |
Methanol reacts with oxygen in a methanol/oxygen fuel cell to form carbon dioxide and water.
Write the balanced symbol equation for this reaction.
Explain why recharging the chemical cell restores it, whereas replacing an empty fuel container allows a fuel cell to continue operating.
Evaluate which fuel cell should be used at the emergency communications station.
Use the information in the table and your own knowledge.
131 exam-style questions on OCR GCSE Chemistry 6.2 Organic chemistry, covering 6.2.1 Crude oil and fractional distillation, 6.2.2 Cracking and dependence on hydrocarbons, 6.2.3 Functional groups and homologous series, 6.2.4 Reactions of alkanes, alkenes and alcohols, 6.2.5 Addition polymerisation and repeat units, 6.2.6 Naturally occurring polymers, 6.2.7 Chemical cells and fuel cells, and 6.2.8 Condensation polymerisation and how to make one. Each one has a worked solution and a mark scheme showing where the marks go.