Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere. Why is ozone gas not produced in this way in the lower atmosphere? The destruction of the ozone layer is a matter of environmental concern. A non-metal oxide and chlorine atoms from CFCs are considered to be mainly responsible for the destruction of ozone. (i) What are CFC molecules? (ii) Why do CFC molecules have long residence times in the lower atmosphere? (iii) Give a major use of CFCs before their production was restricted in 1987. (iv) Name the non-metallic oxide that is associated with ozone destruction in the stratosphere. Give a source of this oxide.

Leaving Cert Chemistry OPTION : Atmospheric Chemistry: Outline the chemical processes t

Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere - Leaving Cert Chemistry - Question B - 2011

Question B

Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere. Why is ozone gas not produced in this way in the lower atmosphere?... show full transcript

Worked Solution & Example Answer:Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere - Leaving Cert Chemistry - Question B - 2011

Step 1

Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere.

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Answer

The process begins with the decomposition of oxygen molecules into oxygen atoms (radicals) through high-energy ultraviolet (UV) light:

$O_2 \xrightarrow{\text{UV light}} 2O$

These oxygen atoms can then react with other oxygen molecules to form ozone:

$O + O_2 \rightarrow O_3$

In summary, ozone is formed from the reaction of super-heated oxygen and UV light.

Step 2

Why is ozone gas not produced in this way in the lower atmosphere?

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Answer

The lack of high-energy ultraviolet (UV) light in the lower atmosphere means that oxygen molecules do not decompose. Thus, ozone is not produced.

Step 3

What are CFC molecules?

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Answer

Chlorofluorocarbons (CFCs) are organic compounds that contain chlorine, fluorine, carbon, and hydrogen. They are primarily used in industrial applications.

Step 4

Why do CFC molecules have long residence times in the lower atmosphere?

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Answer

CFCs are stable and unreactive, meaning they do not readily decompose or react in the lower atmosphere. Their insufficient reactivity leads to their long residence times.

Step 5

Give a major use of CFCs before their production was restricted in 1987.

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Answer

CFCs were primarily used as refrigerants in air-conditioning and refrigeration systems.

Step 6

Name the non-metallic oxide that is associated with ozone destruction in the stratosphere.

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Answer

Nitrogen (N) oxides, such as nitric oxide (NO) or nitrogen monoxide, are non-metallic oxides associated with ozone destruction.

Step 7

Give a source of this oxide.

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Answer

Nitrogen oxides can be produced from electrical discharge (e.g., spark plugs), car engines, and through various combustion processes in urban environments.

Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere - Leaving Cert Chemistry - Question B - 2011

Worked Solution & Example Answer:Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere - Leaving Cert Chemistry - Question B - 2011

Outline the chemical processes that give rise to the occurrence of ozone gas in the stratosphere.

Why is ozone gas not produced in this way in the lower atmosphere?

What are CFC molecules?

Why do CFC molecules have long residence times in the lower atmosphere?

Give a major use of CFCs before their production was restricted in 1987.

Name the non-metallic oxide that is associated with ozone destruction in the stratosphere.

Give a source of this oxide.

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