Ozone depletion and CFCsAQA A-Level Chemistry: Mind map

Exam questions on Ozone depletion and CFCs

1. Ozone, O₃, forms naturally in the upper atmosphere. Dichlorodifluoromethane, CCl₂F₂, is a chlorofluorocarbon (CFC) that was widely used as a refrigerant, and its molecules can drift up into the same region of the atmosphere.
   Write an equation for the formation of a chlorine atom from CCl₂F₂ and state the type of bond fission involved.2 marks
2. Chlorine atoms in the upper atmosphere decompose ozone by a two-step sequence: Cl· + O₃ → ClO· + O₂ ClO· + O₃ → 2O₂ + Cl·
   Explain why one chlorine atom can lead to the decomposition of many ozone molecules.2 marks
3. Until the 1980s CFCs were widely used as solvents and refrigerants. In 1985 researchers working in Antarctica reported unexpectedly low ozone concentrations above the continent. Other research groups, using different measuring methods, then published their own results.
   Explain how the results of research by different groups provided evidence that led to legislation banning CFCs.3 marks