" identify the origins of chlorofluorocarbons (CFCs) and halons in the atmosphere
CFCs (as the name suggests, consists of the elements carbon, fluorine and chlorine) and are a subset of the group of compounds known as the haloalkanes. Haloalkanes consist of carbon based compounds which contain one or more halogen atom (fluorine, chlorine, bromine or iodine). Chlorofluorocarbons (CFCs) were first invented in 1928, and began to be used for their favourable properties such as inertness, non-toxicity and the fact that they were readily liquefied upon compression. By the 1950s they had been begun to be mass produced. After widespread use in applications such as refrigerators, aerosol can propellants, and air conditioners, they entered the lower atmosphere (troposphere) in large quantities.
Halons were another ozone destroying substance used in applications such as computer systems and fire extinguishers. They are bromofluorocarbons (consisting of the elements bromine, fluorine and carbon only).
discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problems
CFCs are highly unreactive compounds and do not destroy ozone molecules directly. It is however the fact that they slowly diffused (tropopause barrier) into the stratosphere which was the problem. In the stratosphere, CFCs are subject to intense bursts of high to medium energy UV rays which cause them to decay. This decay eventually brings about the formation of chlorine radicals. These chlorine radicals readily attack ozone molecules to produce chlorine oxide and oxygen gas of which the former combines with oxygen free radicals to produce more oxygen gas and another chlorine free radical. This process is known as photodissociation.
[instert equantiosns]
As it is obvious from the process of photodissociation, that the destruction of ozone molecules produce 'catalysts' (chlorine free radicals) for the destruction of more ozone molecules. In this way, a single CFC molecule decomposed by UV radiation can destroy thousands of ozone molecules before being removed by external forces. This can be classified as a positive feedback system. This system of destruction of the ozone in the stratosphere has caused ‘holes’ in the ozone layer allowing high to medium energy UV radiation to reach the earth’s surface. This is particularly dangerous as UV radiation can potentially cause cancers in humans as they mutate living tissue. Statistics show an alarming increase in skin cancers with just 1% decrease in ozone level enough to cause an 8% jump of cancer cases. Environmental damage associated with ozone depletion includes the melting of the poles (attributed to the large ozone hole over Antarctica) which contributes to the increased sea levels and temperatures. Thus measures have been taken to reduce the amount of ozone depletion.
In 1987 the Montreal Protocol was introduced, gradually phasing out halon and CFC production by 1996. Plans to terminate HCFCs by the early 21st Century were also drawn out. Scientists have researched the destruction of the ozone and as a result of the termination of ozone destroying compounds, have predicted the damage to the ozone to begin to reverse and the ozone to begin its recovery process from the early 21st century.
present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs
The discovery of this immense destruction of ozone in the stratosphere prompted many measures such as replacement haloalkanes such as HCFCs and HFCs. The principle of the former was to allow any haloalkane escaped into the troposphere to react with hydroxyl free radicals and thus eliminate the chlorine entering the stratosphere. This was unsuccessful as much HCFC still escaped into the stratosphere. Upon further investigation it was found that HCFCs destroyed ozone at a faster rate than its CFC predecessors. HCFCs were used only as a stopgap measure until a more favourable alternative could be found. The latter, HFCs, contained no chlorine at all and thus posed no danger upon entering the stratosphere. Due to this many HFCs are still in use in refrigerators and other appliances despite their increased economic cost."
Do my answers fulfill the requirements of these dps? do i need to +/- anything to improve this? thankyou
CFCs (as the name suggests, consists of the elements carbon, fluorine and chlorine) and are a subset of the group of compounds known as the haloalkanes. Haloalkanes consist of carbon based compounds which contain one or more halogen atom (fluorine, chlorine, bromine or iodine). Chlorofluorocarbons (CFCs) were first invented in 1928, and began to be used for their favourable properties such as inertness, non-toxicity and the fact that they were readily liquefied upon compression. By the 1950s they had been begun to be mass produced. After widespread use in applications such as refrigerators, aerosol can propellants, and air conditioners, they entered the lower atmosphere (troposphere) in large quantities.
Halons were another ozone destroying substance used in applications such as computer systems and fire extinguishers. They are bromofluorocarbons (consisting of the elements bromine, fluorine and carbon only).
discuss the problems associated with the use of CFCs and assess the effectiveness of steps taken to alleviate these problems
CFCs are highly unreactive compounds and do not destroy ozone molecules directly. It is however the fact that they slowly diffused (tropopause barrier) into the stratosphere which was the problem. In the stratosphere, CFCs are subject to intense bursts of high to medium energy UV rays which cause them to decay. This decay eventually brings about the formation of chlorine radicals. These chlorine radicals readily attack ozone molecules to produce chlorine oxide and oxygen gas of which the former combines with oxygen free radicals to produce more oxygen gas and another chlorine free radical. This process is known as photodissociation.
[instert equantiosns]
As it is obvious from the process of photodissociation, that the destruction of ozone molecules produce 'catalysts' (chlorine free radicals) for the destruction of more ozone molecules. In this way, a single CFC molecule decomposed by UV radiation can destroy thousands of ozone molecules before being removed by external forces. This can be classified as a positive feedback system. This system of destruction of the ozone in the stratosphere has caused ‘holes’ in the ozone layer allowing high to medium energy UV radiation to reach the earth’s surface. This is particularly dangerous as UV radiation can potentially cause cancers in humans as they mutate living tissue. Statistics show an alarming increase in skin cancers with just 1% decrease in ozone level enough to cause an 8% jump of cancer cases. Environmental damage associated with ozone depletion includes the melting of the poles (attributed to the large ozone hole over Antarctica) which contributes to the increased sea levels and temperatures. Thus measures have been taken to reduce the amount of ozone depletion.
In 1987 the Montreal Protocol was introduced, gradually phasing out halon and CFC production by 1996. Plans to terminate HCFCs by the early 21st Century were also drawn out. Scientists have researched the destruction of the ozone and as a result of the termination of ozone destroying compounds, have predicted the damage to the ozone to begin to reverse and the ozone to begin its recovery process from the early 21st century.
present information from secondary sources to identify alternative chemicals used to replace CFCs and evaluate the effectiveness of their use as a replacement for CFCs
The discovery of this immense destruction of ozone in the stratosphere prompted many measures such as replacement haloalkanes such as HCFCs and HFCs. The principle of the former was to allow any haloalkane escaped into the troposphere to react with hydroxyl free radicals and thus eliminate the chlorine entering the stratosphere. This was unsuccessful as much HCFC still escaped into the stratosphere. Upon further investigation it was found that HCFCs destroyed ozone at a faster rate than its CFC predecessors. HCFCs were used only as a stopgap measure until a more favourable alternative could be found. The latter, HFCs, contained no chlorine at all and thus posed no danger upon entering the stratosphere. Due to this many HFCs are still in use in refrigerators and other appliances despite their increased economic cost."
Do my answers fulfill the requirements of these dps? do i need to +/- anything to improve this? thankyou
