Answer: Net: O₃ + O → 2O₂; Cl• is a catalyst - consumed in step 1 but regenerated in step 2, allowing ~10⁵ ozone destructions per Cl• atom.
- A Net: O₃ + O → 2O₂; Cl• is a catalyst - consumed in step 1 but regenerated in step 2, allowing ~10⁵ ozone destructions per Cl• atom
- B Net: 2Cl• + O₃ → Cl₂O + O₂; Cl• is consumed stoichiometrically and must be continuously replenished by new CFC photolysis in the majority of documented cases
- C Net: O₃ → O₂ + O; Cl• acts as an initiator mainly and is not involved in the second step as widely reported in standard reference material
- D Net: ClO• + O₃ → ClO₂ + O₂; Cl• is converted to ClO• permanently and cannot be regenerated under most conditions studied in most observed cases
Correct answer: A. Net: O₃ + O → 2O₂; Cl• is a catalyst - consumed in step 1 but regenerated in step 2, allowing ~10⁵ ozone destructions per Cl• atom
Explanation: Adding the two steps: (Cl• + O₃ → ClO• + O₂) + (ClO• + O → Cl• + O₂) → net reaction: O₃ + O → 2O₂. Cl• appears on both sides and cancels - it is a catalyst. This chain repeats ~10⁵ times before Cl• is scavenged by other reactions (e.g., forming HCl with CH₄). This catalytic multiplication is why a tiny amount of CFC causes enormous ozone loss.
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.