Calcium oxide
Powder sample of white calcium oxide
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| Names | |
|---|---|
| IUPAC name
Calcium oxide
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Other names
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| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.013.763 |
| EC Number |
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| E number | E529 (acidity regulators, ...) |
Gmelin Reference
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485425 |
| KEGG | |
PubChem CID
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| RTECS number |
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| UNII | |
| UN number | 1910 |
CompTox Dashboard (EPA)
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SMILES
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| Properties | |
| CaO | |
| Molar mass | 56.0774 g/mol |
| Appearance | White to pale yellow/brown powder |
| Odor | Odorless |
| Density | 3.34 g/cm3[1] |
| Melting point | 2,613 °C (4,735 °F; 2,886 K)[1] |
| Boiling point | 2,850 °C (5,160 °F; 3,120 K) (100 hPa)[2] |
| Reacts to form calcium hydroxide | |
| Solubility in Methanol | Insoluble (also in diethyl ether, octanol) |
| Acidity (pKa) | 12.8 |
Magnetic susceptibility (χ)
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−15.0×10−6 cm3/mol |
| Structure | |
| Cubic, cF8 | |
| Thermochemistry | |
Std molar
entropy (S⦵298) |
40 J·mol−1·K−1[3] |
Std enthalpy of
formation (ΔfH⦵298) |
−635 kJ·mol−1[3] |
| Pharmacology | |
| QP53AX18 (WHO) | |
| Hazards | |
| GHS labelling: | |
Pictograms
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| Danger | |
Hazard statements
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H302, H314, H315, H335 |
Precautionary statements
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P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P330, P332+P313, P362, P363, P403+P233, P405, P501 |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable[4] |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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>2000 mg/kg oral, female rat [5] |
| NIOSH (US health exposure limits): | |
PEL (Permissible)
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TWA 5 mg/m3[4] |
REL (Recommended)
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TWA 2 mg/m3[4] |
IDLH (Immediate danger)
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25 mg/m3[4] |
| Safety data sheet (SDS) | ICSC 0409 |
| Related compounds | |
Other anions
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Other cations
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Calcium oxide (formula: CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term lime connotes calcium-containing inorganic compounds, in which carbonates, oxides, and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, quicklime specifically applies to the single compound calcium oxide. Calcium oxide that survives processing without reacting in building products, such as cement, is called free lime.[6]
Quicklime is relatively inexpensive. Both it and the chemical derivative calcium hydroxide (of which quicklime is the base anhydride) are important commodity chemicals.
- ^ a b Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, Florida: CRC Press. p. 4.55. ISBN 1-4398-5511-0.
- ^ Calciumoxid (Archived 2013-12-30 at the Wayback Machine). GESTIS database
- ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 978-0-618-94690-7.
- ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0093". National Institute for Occupational Safety and Health (NIOSH).
- ^ "Safety Data Sheet: Calcium Oxide". ThermoFisher Scientific. p. 5. Retrieved 12 September 2025.
- ^ "free lime". DictionaryOfConstruction.com. Archived from the original on 2017-12-09.