Calcium hydride
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Calcium hydride is the chemical compound with the formula CaH2, an alkaline earth hydride. This grey powder (white if pure, which is rare) reacts vigorously with water liberating hydrogen gas. CaH2 is thus used as a drying agent, i.e. a desiccant.[2]
Quick Facts Names, Identifiers ...
Names | |
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IUPAC name
Calcium hydride | |
Other names
Calcium(II) hydride Calcium dihydride Hydrolith | |
Identifiers | |
3D model (JSmol) |
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ChemSpider |
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ECHA InfoCard | 100.029.263 |
EC Number |
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PubChem CID |
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UNII | |
CompTox Dashboard (EPA) |
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Properties | |
CaH2 | |
Molar mass | 42.094 g/mol |
Appearance | gray powder (white when pure) |
Density | 1.70 g/cm3, solid |
Melting point | 816 °C (1,501 °F; 1,089 K) |
reacts violently | |
Solubility | reacts in alcohol |
Structure | |
Orthorhombic, oP12 | |
Pnma, No. 62 | |
Thermochemistry | |
Std molar entropy (S⦵298) |
41.4 J·mol−1·K−1[1] |
Std enthalpy of formation (ΔfH⦵298) |
−181.5 kJ·mol−1 |
Gibbs free energy (ΔfG⦵) |
-142.5 kJ/mol |
Hazards | |
GHS labelling: | |
Danger | |
H260 | |
NFPA 704 (fire diamond) | |
Related compounds | |
Other cations |
Sodium hydride, Potassium hydride Magnesium hydride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Close
CaH2 is a saline hydride, meaning that its structure is salt-like. The alkali metals and the alkaline earth metals heavier than beryllium all form saline hydrides. A well-known example is sodium hydride, which crystallizes in the NaCl motif. These species are insoluble in all solvents with which they do not react. CaH2 crystallizes in the PbCl2 (cotunnite) structure.[3]