A-Level AQA Chemistry Organic Mechanisms: This question is about the ozone

Question

This question is about the ozone layer in the upper atmosphere.

1. State why the ozone layer is beneficial for living organisms.
   The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun, which helps to prevent skin cancer and other health issues in living organisms.

2. State how chlorofluorocarbons (CFCs) form chlorine atoms in the upper atmosphere.
   In the upper atmosphere, CFCs undergo photodissociation under UV light, breaking down to release chlorine atoms.

3. Give equations to show how chlorine atoms catalyse the decomposition of ozone.
   The decomposition of ozone by chlorine atoms can be represented by the following reactions:
   $$Cl^\cdot + O_3 \rightarrow ClO^\cdot + O_2$$
   $$ClO^\cdot + O \rightarrow Cl^\cdot + O_2$$
   In these equations, a chlorine radical reacts with ozone to form chlorine monoxide, which further reacts to regenerate the chlorine radical and produce more oxygen.

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.
   $$ \cdot CHF_2 + Cl_2 \rightarrow CHF_2Cl + \cdot Cl$$
   $$ \cdot CH_3 + Cl_2 \rightarrow CH_3Cl + \cdot Cl$$
   Give the name of the type of step shown by both these equations.
   The steps shown are examples of propagation steps in the mechanism.

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

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.

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