Photolysis of Water (Vacuum UV)
H2O → H· + OH·
Overview
Vacuum UV radiation (< 185 nm) directly dissociates water molecules into hydrogen and hydroxyl radicals. This reaction is significant in atmospheric chemistry on Mars and early Earth, where the photolysis of water vapor contributed to the loss of hydrogen to space and the oxidation of surface minerals.
Participants
| Role | Substance | Coefficient | State |
|---|---|---|---|
| Reactant | Water H₂O | 1 | (g) |
Everyday Example
Mars lost most of its water over billions of years partly because UV photolysis split water vapor in the upper atmosphere.
Industrial Importance
Vacuum UV water photolysis is used in ultrapure water treatment for semiconductor manufacturing and in space environment simulation.
Properties
- Type
- Photochemical
- Reversible
- No
- Energy
- Endothermic
- ΔH
- 498.0 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
Ozone Formation by UV Light
Photocatalytic NOx Removal
Photocatalytic Water Splitting (TiO₂)
Photochemical Cycloaddition ([2+2])
Frequently Asked Questions
What is the equation for Photolysis of Water (Vacuum UV)?
The balanced equation is: H₂O → H· + OH·.
What type of reaction is Photolysis of Water (Vacuum UV)?
Photolysis of Water (Vacuum UV) is a photochemical reaction.
Is Photolysis of Water (Vacuum UV) exothermic or endothermic?
Photolysis of Water (Vacuum UV) is endothermic (absorbs energy). The enthalpy change (ΔH) is 498.0 kJ/mol.