Properties of Ozone (O₃)
Ozone (O₃) is an allotrope of oxygen with distinct chemical properties that make it both useful and hazardous.
1. Molecular Structure
- Formula: O₃
- Bond angle: ~116.8° (bent shape)
- Resonance structure: Ozone has two resonance forms, meaning the bonding electrons are delocalized between the three oxygen atoms.
2. Physical Properties
- Color: Pale blue gas (dark blue in liquid form)
- Odor: Sharp, pungent smell (detectable at 0.01 ppm)
- Density: 2.14 g/L (heavier than oxygen: 1.43 g/L)
- Boiling point: -111.9°C (-169.4°F)
- Melting point: -192.2°C (-314°F)
3. Reactivity & Oxidation
- Strong oxidizer: Ozone is one of the most powerful oxidizing agents, with an oxidation potential of 2.07 V (higher than chlorine’s 1.36 V).
- Reaction with metals:
- Reacts with silver, lead, and other metals to form oxides.
- Does not react with gold or platinum.
- Reaction with organic compounds:
- Ozonolysis: Breaks down alkenes and alkynes into carbonyl compounds (aldehydes, ketones, or acids).
- Decomposition:
- Naturally decomposes to O₂ at room temperature: 2O3→3O22O₃ \rightarrow 3O₂
- Accelerated by heat, UV light, or catalysts like manganese dioxide (MnO₂).
4. Solubility
- In Water: ~0.64 g/L at 0°C (more soluble than oxygen).
- In Organic Solvents: Soluble in carbon tetrachloride (CCl₄) and fluorocarbons.
5. Stability
- Unstable at higher temperatures and pressures.
- Short half-life (~20-30 minutes at room temperature).
- Quickly reverts to oxygen gas (O₂) in normal conditions.