This question is about the ozone layer in the upper atmosphere. 1. State why the ozone layer is beneficial for living organisms. --- 2. State how chlorofluorocarbons (CFCs) form chlorine atoms in the upper atmosphere. --- 3. Give equations to show how chlorine atoms catalyse the decomposition of ozone. --- 4. Hydrochlorofluorocarbons (HCFCs) have been used in place of CFCs. In the mechanism to make an HCFC from a fluoroalkane, two incomplete steps are shown. Complete each step in the mechanism. Give the name of the type of step shown by both these equations. --- → CHF2 + HCl → CHF3 + Cl• Type of step

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This question is about the ozone layer in the upper atmosphere - AQA - A-Level Chemistry - Question 9 - 2021 - Paper 2

Question 9

This question is about the ozone layer in the upper atmosphere. 1. State why the ozone layer is beneficial for living organisms. --- 2. State how chlorofluorocarb... show full transcript

Worked Solution & Example Answer:This question is about the ozone layer in the upper atmosphere - AQA - A-Level Chemistry - Question 9 - 2021 - Paper 2

Step 1

State why the ozone layer is beneficial for living organisms.

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Answer

The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun, thereby preventing skin cancer and protecting ecosystems.

Step 2

State how chlorofluorocarbons (CFCs) form chlorine atoms in the upper atmosphere.

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Answer

Chlorofluorocarbons (CFCs) undergo photodissociation in the upper atmosphere, breaking down into chlorine atoms.

Step 3

Give equations to show how chlorine atoms catalyse the decomposition of ozone.

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Answer

Cl• + O3 → ClO• + O2
ClO• + O → Cl• + O2

The chlorine atom acts as a catalyst, being regenerated in the process.

Step 4

Complete each step in the mechanism.

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Answer

Cl• + CHF3 → CHF2Cl + H•
CHF2Cl → CHF3 + Cl•

The type of step shown by both equations is 'Propagation'.

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This question is about the ozone layer in the upper atmosphere - AQA - A-Level Chemistry - Question 9 - 2021 - Paper 2

Worked Solution & Example Answer:This question is about the ozone layer in the upper atmosphere - AQA - A-Level Chemistry - Question 9 - 2021 - Paper 2

State why the ozone layer is beneficial for living organisms.

State how chlorofluorocarbons (CFCs) form chlorine atoms in the upper atmosphere.

Give equations to show how chlorine atoms catalyse the decomposition of ozone.

Complete each step in the mechanism.

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