In the South Pole, the sun disappears in winter and a vortex of cold air forms. This cause clouds to be formed in the stratosphere and they are usually frozen sulphuric acid with nitric acid trihydrate (HNO3i?? 3H2O) coated around them. At 190K, water vapour will condense as ice on these particles as well. This Solid particle provides a surface on which this occurs: HCl + ClONO2 –> Cl2 + HNO3 Chlorine will be released. As the sun comes back in spring, the radiation will cause this to occur: Cl2 + hv –> 2Cli?? This will cause an even more severe Ozone depletion due to more Cli?? being around in the stratosphere. CFCS AND THEIR REPLACEMENTS.

CFC were considered better than ammonia, CO2, water, propane or SO2, which are some of the early refrigerants available. They either had an unsuitable boiling point which increased the cost and size of the equipment dramatically, or were too inflammable for safe use. Some were even toxic and required special handling procedures. So therefore this is the reason why CFCs where widely used, and because of the thermal insulation properties of some CFCs and their chemical inertness, they also found use in areas as diverse as blowing insulating-foam, cleaning agent for printed circuit-boards, dry-cleaning and as propellant for aerosol cans.

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It was almost possible to find a CFC for every application. When CFCs’ destructive effects were discovered, there were no known replacements, but it was soon found that HFCs (hydro fluorocarbons), a closely related series of compounds, had most of the wonderful qualities. HFCs don’t destroy ozone because fluorine is strongly bound to the carbon and even the energy given by ultraviolet rays is not enough to liberate the fluorine. Some of these replacements have less energy efficiency than the original CFCs.

HFCs are also used as a replacement in the short term – they again have similar properties to CFC but they can still cause small amounts of ozone depletion. The cost for manufacturing HFCs are higher then CFCs as was equipment is needed to suit the properties of HFCs (equipment needed to work at slightly higher pressures). In some cases, a replacement is not even needed at all – many aerosols are being replaced by air pumps or electrostatic charged sprays. This reduces the amount of chemical released into the atmosphere. But they are expensive to implement and are inconvenient.

ABSTRACT Scientists have linked that the use of CFCs the release of chlorine radicals which destroy the steady state of ozone and oxygen, this was done though such methods as spectroscopy and flash photolysis. CFCs were used in refrigeration, aerosols and cleaning products. HFCs where introduced but there were some difficulties in doing this. Bibliography Main References – the summary is based closely on the following articles. M. Pilling et al. , ‘How do we know that CFCs destroy the ozone layer? ‘, Chemistry Review, Vol. 3, Nr.4, March 1993, Philip Allan Publishers (York). R.

Powell, ‘The rise and fall of CFCs’, Chemistry Review, Vol. 6, Nr. 1, September 1996, Philip Allan Publishers (York). Specific References [1] G. Burton et al. , Salters Advanced Chemistry: Chemical Ideas, pp. 119-120, Heinemann Educational Publishers (1994, York). Word Count: 922 words Altaf Korimbocus Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

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