H₂O
Compound · Oxide
Water
水
Water (水), formula H₂O, is a oxide with a molar mass of 18.02 g/mol (CAS 7732-18-5). Colourless, odourless, transparent liquid; itself the "universal solvent"; dissolves many polar substances.
Key facts
| Molar mass | 18.02 g/mol |
|---|---|
| Category | Oxide |
| State at 25°C | Liquid |
| CAS | 7732-18-5 |
Structure
H–O–H
Bent, bond angle ≈ 104.5°, strongly polar
Physical properties
| Appearance | Colourless, odourless, transparent liquid |
|---|---|
| Melting point | 0 °C |
| Boiling point | 100 °C |
| Density | 1.00 g/cm³ (4 °C) |
| Solubility | Itself the "universal solvent"; dissolves many polar substances |
Key reactions
2Na + 2H₂O → 2NaOH + H₂↑
Reacts with active metals, releasing hydrogen
CO₂ + H₂O ⇌ H₂CO₃
Combines with acidic oxides to form the corresponding acid
2H₂O →(电解) 2H₂↑ + O₂↑
Electrolyses into hydrogen and oxygen
Main uses
- Foundation of all life
- Industrial cooling, cleaning and solvent
- Hydropower and transport
Hazard
LowNon-toxic; high-temperature steam can scald
Constituent elements
Data sources
Molar mass is computed from IUPAC (CIAAW) standard atomic weights; formula, properties and reactions can be verified on PubChem, NIST and Wikipedia. The CAS number is the substance's unique registry identifier. Educational reference only.