← All topics
Global & Regional Environmental Issues
Ozone Depletion & Acid Rain
Stratospheric ozone, ODP, the Montreal Protocol and the chemistry of acid deposition.
PART 1
Topic Breakdown & Traps
The Engineering Principle
Stratospheric ozone shields the surface from harmful UV-B. Chlorofluorocarbons (CFCs), halons and CCl₄ release chlorine/bromine that catalytically destroy ozone; their potency is the Ozone Depletion Potential (ODP), normalised to CFC-11 = 1. The Montreal Protocol phases out these substances. Acid rain forms when SO₂ and NOₓ oxidise to sulphuric and nitric acids, lowering precipitation pH below the natural ≈ 5.6.
The Core Formula Matrix
Ozone Depletion Potential: ODP defined relative to CFC-11 = 1.0.
Montreal Protocol (1987): phases out ozone-depleting substances (ODS).
Natural rain pH ≈ 5.6 (dissolved CO₂ → carbonic acid).
Acid rain precursors: SO₂ → H₂SO₄; NOₓ → HNO₃ (pH < 5.6).
Montreal Protocol (1987): phases out ozone-depleting substances (ODS).
Natural rain pH ≈ 5.6 (dissolved CO₂ → carbonic acid).
Acid rain precursors: SO₂ → H₂SO₄; NOₓ → HNO₃ (pH < 5.6).
The ‘IIT Traps’
- ⚠ODP is referenced to CFC-11, while GWP is referenced to CO₂ — different baselines.
- ⚠CO₂ is a GHG, not an ozone-depleting substance.
- ⚠Even clean rain is mildly acidic (pH ≈ 5.6) from dissolved CO₂ — acid rain is below that.
📚 Standard references
- Environmental Chemistry — A.K. De · Atmospheric Chemistry
PART 2
Progressive 3-Tier Question Suite
Q1BASIC1 Mark · MCQ
The Ozone Depletion Potential (ODP) of a substance is measured relative to:
Q2MEDIUM1 Mark · MCQ
The international agreement responsible for phasing out ozone-depleting substances is the:
Q3HARD2 Marks · MCQ
Unpolluted rainwater is naturally mildly acidic (pH ≈ 5.6) because of dissolved: