10.2.3Air and the Environment
Reducing the Effects of Environmental Issues — Combined Science 0653 - Chemistry Revision Notes & Topical Questions
5 min read 7 parts Lesson 7 of 7 Unit quiz
Part 1 of 5Cutting greenhouse gases
Use cleaner energy
- Use cleaner energy Switch from burning fossil fuels to hydrogen, solar power and wind power,
- which do not release carbon dioxide when generating energy.
Travel and use less
- Travel and use less Use fuel-efficient, electric or hybrid cars, share journeys or take public transport,
- and reduce household energy use with efficient appliances.
Recycle and reuse
- Recycle and reuse Recycling products made from crude oil, such as plastics, saves the fuel that would be needed to make new ones.
Look after forests
- Look after forests Stopping deforestation and planting new trees removes carbon dioxide from the air by photosynthesis.
Reduce methane
- Reduce methane Keeping fewer livestock reduces the methane released during animal digestion.
Part 2 of 5Reducing acid rain
Cut SO2 and nitrogen oxides
Cleaner fuels
- Cleaner fuels Burning fuels that contain very little sulfur means less sulfur dioxide is produced in the first place.
Flue gas desulfurisation
- Flue gas desulfurisation The main method for stopping sulfur dioxide leaving power station chimneys.
Catalytic converters
- Catalytic converters Fitted to vehicle exhausts to remove oxides of nitrogen.
Part 3 of 5Flue gas desulfurisation in a coal-fired power station
1
Waste gases from the furnace are sent into a scrubbing chamber before reaching the chimney.
2
A wet slurry of calcium oxide and calcium carbonate is sprayed over the gases.
3
These basic calcium compounds react with the acidic sulfur dioxide to form calcium sulfate.
4
Around 90 to 95% of the sulfur dioxide is removed, so far less acid rain is produced.
Part 4 of 5Catalytic converters (extended tier)
Why they are needed
- Why they are needed Nitrogen and oxygen react at the high temperature and pressure in an engine, producing NO and NO2.
- The exhaust also contains carbon monoxide and unburnt hydrocarbons.
Construction
- Construction Transition metal catalysts such as platinum and rhodium are spread over a honeycomb, which gives a very large surface area for reaction.
Redox reactions
- Redox reactions Carbon monoxide is oxidised to carbon dioxide: 2CO + O2 → 2CO2.
- Oxides of nitrogen are reduced to nitrogen gas, and the overall reaction is 2NO + 2CO → N2 + 2CO2.
- Unburnt hydrocarbons are oxidised to carbon dioxide and water.
Part 5 of 5Pollutant and matching strategy
| Problem | Cause | Strategy |
|---|---|---|
| Climate change | Carbon dioxide and methane | Renewable energy, fewer vehicles, tree planting, fewer livestock |
| Acid rain from sulfur dioxide | Burning sulfur-containing fuels | Low-sulfur fuel, flue gas desulfurisation |
| Acid rain from nitrogen oxides | High-temperature engines | Catalytic converters |
Key terms
| Term | Meaning |
|---|---|
| Climate change | Long-term change in global temperatures and weather patterns caused largely by increased greenhouse gases. |
| Reforestation | Planting trees to replace those that have been cut down. |
| Flue gas desulfurisation | Removing sulfur dioxide from power station waste gases using a calcium compound slurry. |
| Catalytic converter | An exhaust fitting containing metal catalysts that turns harmful gases into harmless ones. |
| Redox reaction | A reaction in which oxidation and reduction happen at the same time. |
Avoid these mistakes
1
Suggesting catalytic converters reduce carbon dioxide. They convert carbon monoxide, nitrogen oxides and hydrocarbons into less harmful gases, and they actually produce carbon dioxide.
2
Saying scrubbers use acid. The slurry is basic (calcium oxide and calcium carbonate) so that it neutralises acidic sulfur dioxide.
3
Writing that trees remove methane. Trees take in carbon dioxide during photosynthesis.
4
Forgetting why the converter is a honeycomb: it provides a large surface area for the catalyst.
5
Mixing up the two problems. Greenhouse gases cause climate change whereas sulfur dioxide and nitrogen oxides cause acid rain.
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