Calcium oxide is a chemical compound of calcium and oxygen. Its chemical formula is CaO. It is known as quicklime. It is made in a lime kiln. It releases heat when dissolved in water and changes into calcium hydroxide. It is a white powder.
Quick facts Names, Identifiers ...
Calcium oxide
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| Names |
| IUPAC name
Calcium oxide |
| Other names
Quicklime, burnt lime, unslaked lime, pebble lime, calcia |
| Identifiers |
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3D model (JSmol) |
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| ChEBI |
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| ChEMBL |
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| ChemSpider |
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| ECHA InfoCard |
100.013.763 |
| E number |
E529 (acidity regulators, ...) |
| Gmelin Reference |
485425 |
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| RTECS number |
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| UNII |
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| UN number |
1910 |
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| Properties |
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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 |
|
−15.0×10−6 cm3/mol |
| Structure |
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Cubic, cF8 |
| Thermochemistry |
Std enthalpy of
formation ΔfHo298 |
−635 kJ·mol−1[3] |
Standard molar
entropy So298 |
40 J·mol−1·K−1[3] |
| Pharmacology |
ATCvet code |
QP53AX18 (WHO) |
| Hazards |
| NFPA 704 |
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| Flash point |
Non-flammable |
U.S. Permissible
exposure limit (PEL) |
TWA 5 mg/m3[4] |
| Related compounds |
| Other anions |
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| Other cations |
{{{value}}} |
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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It is also a base. It reacts with acids to make calcium salts. Quicklime is an important ingredient of cement.
