Ca(OH)₂
Compound · Base
Calcium hydroxide
氢氧化钙 (熟石灰)
Calcium hydroxide (氢氧化钙 (熟石灰)), formula Ca(OH)₂, is a base with a molar mass of 74.09 g/mol (CAS 1305-62-0). White powder; slightly soluble; solubility decreases as temperature rises.
Key facts
| Molar mass | 74.09 g/mol |
|---|---|
| Category | Base |
| State at 25°C | Solid |
| CAS | 1305-62-0 |
Structure
Ca²⁺ (OH⁻)₂
Sparingly soluble strong base; its solution is limewater
Physical properties
| Appearance | White powder |
|---|---|
| Melting point | 580 °C (分解) |
| Boiling point | — |
| Density | 2.21 g/cm³ |
| Solubility | Slightly soluble; solubility decreases as temperature rises |
Key reactions
Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O
Limewater turns milky — the CO₂ test
Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O
Neutralisation with acid
Main uses
- Mortar and plastering
- Neutralising acidic soils
- Wastewater treatment and flue-gas desulfurisation
Hazard
ModerateAlkaline; irritates skin and eyes
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.