| Identifiers | |
|---|---|
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3D model (Jmol)
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| ChemSpider | |
| ECHA InfoCard | 100.028.623 |
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PubChem CID
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| RTECS number | OJ6300000 |
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| Properties | |
| LiH | |
| Molar mass | 7.95 g/mol |
| Appearance | colorless to gray solid |
| Density | 0.78 g/cm3 |
| Melting point | 688.7 °C (1,271.7 °F; 961.9 K) |
| Boiling point | decomposes at 900–1000 °C |
| reacts | |
| Solubility | slightly soluble in dimethylformamide reacts with ammonia, diethyl ether, ethanol |
| −4.6·10−6 cm3/mol | |
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Refractive index (nD)
|
1.9847 |
| Structure | |
| fcc (NaCl-type) | |
|
a = 0.40834 nm
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| 6.0 D | |
| Thermochemistry | |
| 3.51 J/(g·K) | |
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Std molar
entropy (S |
170.8 J/mol K |
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Std enthalpy of
formation (ΔfH |
-90.65 kJ/mol |
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Gibbs free energy (ΔfG˚)
|
-68.48 kJ/mol |
| Hazards | |
| Safety data sheet | ICSC 0813 |
| NFPA 704 | |
| 200 °C (392 °F; 473 K) | |
| Lethal dose or concentration (LD, LC): | |
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LD50 (median dose)
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77.5 mg/kg (oral, rat) |
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LC50 (median concentration)
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22 mg/m3 (rat, 4 hr) |
| US health exposure limits (NIOSH): | |
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PEL (Permissible)
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TWA 0.025 mg/m3 |
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REL (Recommended)
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TWA 0.025 mg/m3 |
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IDLH (Immediate danger)
|
0.5 mg/m3 |
| Related compounds | |
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Other cations
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Sodium hydride Potassium hydride Rubidium hydride Caesium hydride |
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Related compounds
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Lithium borohydride Lithium aluminium hydride |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
Lithium hydride is an inorganic compound with the formula LiH. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like, or ionic, hydride, it has a high melting point and is not soluble but reactive with all organic and protic solvents; it is soluble and non-reactive with certain molten salts such as lithium fluoride, lithium borohydride, and sodium hydride. With a molecular mass of slightly less than 8, it is the lightest ionic compound.
LiH is a diamagnetic and an ionic conductor with a conductivity gradually increasing from 2×10−5 Ω−1cm−1 at 443 °C to 0.18 Ω−1cm−1 at 754 °C; there is no discontinuity in this increase through the melting point. The dielectric constant of LiH decreases from 13.0 (static, low frequencies) to 3.6 (visible light frequencies). LiH is a soft material with a Mohs hardness of 3.5. Its compressive creep (per 100 hours) rapidly increases from < 1% at 350 °C to > 100% at 475 °C meaning that LiH can't provide mechanical support when heated.
The thermal conductivity of LiH decreases with temperature and depends on morphology: the corresponding values are 0.125 W/(cm·K) for crystals and 0.0695 W/(cm·K) for compacts at 50 °C, and 0.036 W/(cm·K) for crystals and 0.0432 W/(cm·K) for compacts at 500 °C. The linear thermal expansion coefficient is 4.2×10−5/°C at room temperature.
LiH is produced by treating lithium metal with hydrogen gas: