Ozone Formation by UV Light
3O2 → 2O3
Overview
Ultraviolet radiation (wavelength < 240 nm) splits O₂ molecules in the stratosphere. The resulting oxygen atoms combine with intact O₂ to form ozone (O₃). This Chapman cycle creates the ozone layer at 15–35 km altitude, which absorbs 97–99% of UV-B and UV-C radiation that would otherwise damage DNA.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Product | Ozone O₃ | 2 | (g) |
Everyday Example
The ozone layer protects life on Earth from harmful UV radiation. Without it, rates of skin cancer and cataracts would skyrocket.
Industrial Importance
The Montreal Protocol (1987) banned CFCs that destroy ozone. Ozone generators are used for water purification and air treatment.
Properties
- Type
- Photochemical
- Reversible
- Yes
- Energy
- Endothermic
- ΔH
- 285.4 kJ/mol
Related Reactions
Chlorophyll Fluorescence
Cis-Trans Isomerization of Retinal
Dye-Sensitized Solar Cell (Grätzel Cell)
Firefly Bioluminescence (Luciferin Oxidation)
Luminol Chemiluminescence
Ozone Decomposition by UV
Photocatalytic NOx Removal
Photocatalytic Water Splitting (TiO₂)
Photochemical Cycloaddition ([2+2])
Photochemical Smog Formation (NO₂ Photolysis)
Frequently Asked Questions
What is the equation for Ozone Formation by UV Light?
The balanced equation is: 3O₂ → 2O₃.
What type of reaction is Ozone Formation by UV Light?
Ozone Formation by UV Light is a photochemical reaction. It is reversible under certain conditions.
Is Ozone Formation by UV Light exothermic or endothermic?
Ozone Formation by UV Light is endothermic (absorbs energy). The enthalpy change (ΔH) is 285.4 kJ/mol.