HNO₃
Compound · Acid
Nitric acid
硝酸
Nitric acid (硝酸), formula HNO₃, is a acid with a molar mass of 63.01 g/mol (CAS 7697-37-2). Colourless liquid; concentrated acid is faintly yellow; miscible with water in all proportions.
Key facts
| Molar mass | 63.01 g/mol |
|---|---|
| Category | Acid |
| State at 25°C | Liquid |
| CAS | 7697-37-2 |
Structure
HO–NO₂
Planar structure; nitrogen in the +5 state
Physical properties
| Appearance | Colourless liquid; concentrated acid is faintly yellow |
|---|---|
| Melting point | −42 °C |
| Boiling point | 83 °C |
| Density | 1.51 g/cm³ |
| Solubility | Miscible with water in all proportions |
Key reactions
HNO₃ + NaOH → NaNO₃ + H₂O
Neutralisation with base
3Cu + 8HNO₃(稀) → 3Cu(NO₃)₂ + 2NO↑ + 4H₂O
Dilute acid oxidises copper, releasing NO
Cu + 4HNO₃(浓) → Cu(NO₃)₂ + 2NO₂↑ + 2H₂O
Concentrated acid releases brown NO₂
Main uses
- Fertiliser and nitrate production
- Explosives feedstock (TNT, nitroglycerin)
- Organic nitration, metal treatment
Hazard
HighCorrosive oxidiser; burns skin and evolves toxic nitrogen oxides
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.