CFCs
Outline of why CFCs were used, what the problems are and the alternatives.
- Created by: Rebecca Neal
- Created on: 28-04-13 08:30
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- CFCs
- History of CFCs
- They were first use in the 1930s.
- They are chemically stable, odourless, non-toxic, non-flammable, easily compressed, have low boiling points (evaporate efficiently) and have low freezing points so they don't turn into solids very easily.
- This makes them very useful as refridgerents.
- Also, propellents in aerosol cans, as blowing agents for expanded polystyrene and as dry cleaning solvents.
- The problems with CFCs
- Some of them reached the stratosphere and began to photodissociate.
- CCl3F + hv -> CClF + Cl
- They are also reformed, leading to a chain reaction.
- Huge amounts of CFCs were used, putting lots of Cl radicals into the stratosphere.
- CFCs are estimated to have a lifetime in the troposphere of approximately 100 years.
- Alternatives
- HCFCs and HFCs
- H-C bonds are broken in the troposphere before they have a chance to reach the stratosphere.
- But are greenhouse gases
- Alkanes
- Do not contain chlorine
- But are greenhouse gases
- HCFCs and HFCs
- History of CFCs
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