This question is about the ozone layer and atmospheric organic chemistry.
Explain how the stratospheric ozone layer serves as a protective shield for living organisms on Earth.
Hydrochlorofluorocarbons (HCFCs) such as chlorodifluoromethane (CHClF2\text{CHClF}_2CHClF2) have been used as transitional replacements for CFCs. Describe how a molecule of chlorodifluoromethane forms chlorine atoms in the upper atmosphere.
Write two equations to show how chlorine atoms (Cl∙\text{Cl}^\bulletCl∙) catalyse the decomposition of ozone (O3\text{O}_3O3).
HCFCs can be synthesised in the laboratory via the free-radical substitution of fluoroalkanes. In the mechanism to make chlorodifluoromethane (CHClF2\text{CHClF}_2CHClF2) from difluoromethane (CH2F2\text{CH}_2\text{F}_2CH2F2), two incomplete steps are shown below.
Complete each step in the mechanism:
......................................................→∙CHF2+HCl \text{......................................................} \rightarrow {}^\bullet\text{CHF}_2 + \text{HCl} ......................................................→∙CHF2+HCl ∙CHF2+Cl2→...................................................... {}^\bullet\text{CHF}_2 + \text{Cl}_2 \rightarrow \text{......................................................} ∙CHF2+Cl2→......................................................Give the name of the type of step represented by both of these equations.
25 exam-style questions on AQA A Level Chemistry Halogenoalkanes, covering Nucleophilic substitution, Elimination, and Ozone depletion. Each one has a worked solution and a mark scheme showing where the marks go.