Calcium oxide
A member of the class of calcium oxides of calcium and oxygen in a 1:1 ratio. — ChEBI
Safety documents & references
2 indexed referencesFind a product-specific SDS
Safety guides and government classification records are not a manufacturer’s SDS. Match supplier, product number, concentration, physical form, region and revision before using a document.
Identity & molecular properties
Source-linked values| CAS number | 1305-78-8 | ChEBI ↗ |
| Molecular formula | Ca.O | ChEBI ↗ |
| Molar mass | 56.077 g/mol | ChEBI ↗ |
| Monoisotopic mass | 55.95751 Da | ChEBI ↗ |
| Formal charge | 0 | ChEBI ↗ |
| ChEBI identifier | CHEBI:31344 | ChEBI ↗ |
Cross-source molecular data
PubChem| Molar mass | 56.08 g/mol | PubChem ↗ |
| Exact mass | 55.9575055 Da | PubChem ↗ |
PubChem computed values are shown separately from the ChEBI record. An exact InChIKey match was used to connect the records. Molecular descriptors do not describe a supplied product’s purity, particle size or performance.
Names & structural identifiers
Copy any identifiercalcium oxidecalcium oxideBRPQOXSCLDDYGP-UHFFFAOYSA-N[Ca+2].[O-2]InChI=1S/Ca.O/q+2;-2Classification & relationships
ChEBI ontologyRoles recorded in ChEBI
Database role annotations describe reported biological or chemical roles; they are not product approvals or recommendations for use.
Safety classification · Japan
NITE / Japanese governmentQuicklime [Calcium oxide] · H28-B-011, C-014B
| Endpoint | Reported classification |
|---|---|
| Skin corrosion/irritation | Category 2 |
| Serious eye damage/eye irritation | Category 1 |
| Specific target organ toxicity - Single exposure | Category 1 (respiratory organs) |
| Specific target organ toxicity - Repeated exposure | Category 1 (respiratory organs) |
Selected source-reported endpoints. Other endpoints, rationales and conditions remain in the original classification. Missing or unlisted information does not mean non-hazardous. This is not a global classification or transport decision.
Read the original NITE classificationMass ↔ amount of substance
Calculated from sourced massUses 56.077 g/mol from ChEBI. Assumes the substance described by this record; no purity or concentration correction is applied.
Elemental composition
Theoretical mass fractionsCaOCalculated theoretical mass fractions from the reported formula and PubChem periodic-table atomic masses. These are not assay or purity results.
Research & patent references
Selected source associationsSources & record history
Checked 27 Sep 2026Release 255, 9 September 2026. ChEBI three-star (manually annotated) source entry. View original record ↗ · CC BY 4.0
PubCAS formats source data, connects references and computes explicitly labelled conversions. CAS cross-references are supplied by ChEBI; they do not constitute CAS verification or endorsement.