Difference between revisions of "Lithium hydride"

Revision as of 13:01, 3 November 2019

Lithium hydride

Crystallized LiH. It's blue not because of the reflection of the glove color, but because lithium hydride turns blue as it ages.
Names
IUPAC name Lithium hydride
Other names Lithium monohydride
Properties
Chemical formula	LiH
Molar mass	7.95 g/mol
Appearance	White or light gray samples
Odor	Odorless
Density	0.78 g/cm3
Melting point	688.7 °C (1,271.7 °F; 961.9 K)
Boiling point	900 °C (1,650 °F; 1,170 K) (decomposes)
Solubility in water	Reacts
Solubility	Reacts with alcohols, aldehydes, amines, ammonia, carboxylic acids, DMSO, esters, ethers, halocarbons, ketones Soluble in molten lithium borohydride, lithium fluoride and sodium hydride Slightly soluble in dimethylformamide Insoluble in hydrocarbons
Vapor pressure	~0 mmHg
Thermochemistry
Std molar entropy (So298)	170.8 J·mol-1K-1
Std enthalpy of formation (ΔfHo298)	-90.65 kJ/mol
Hazards
Safety data sheet	Sigma-Aldrich
Related compounds
Related compounds	Sodium hydride Calcium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Lithium hydride is an inorganic compound with the formula LiH.

Properties

Chemical

Lithium hydride reacts with water to release hydrogen.

LiH + H₂O → LiOH + H₂

Physical

Lithium hydride is an odorless white or slight grayish solid, which reacts with most solvents and is insoluble in those with which it doesn't react, like hydrocarbons.

Availability

Lithium hydride is sold by chemical suppliers, though it's not cheap, and it's hard to find.

On Alibaba one can find many sellers selling what is described as "lihium hydride", but be very careful if you want to purchase the product from there, since most of the prices listed for this compound are very low, which may be suspicious, since lithium compounds aren't cheap, let alone a hydrogen-rich and potentially pyrophoric powdered lithium compound.

Preparation

Can be prepared by reacting molten lithium metal with hydrogen. The reaction takes place in a nickel crucible, between 450-500 °C, and the hydrogen used must be air and water-free. The yield of this reaction is 95%.^[1]

However, the reaction can proceed at temperatures as low as 29 °C. The yield is 60% at 99 °C and 85% at 125 °C, and the rate depends significantly on the surface condition of LiH and the purity of the inert gas used as inert conditions.

Hydrogenolysis of n-butyllithium at normal temperature and atmospheric pressure in the absence of catalyst will yield LiH.^[2]

Projects

• Desiccant
• Make lithium aluminium hydride

Handling

Safety

Lithium hydride is very reactive towards most common solvents, it will even slowly attack ethers. It may spontaneously ignite in moist air.

Storage

Lithium hydride must be kept in air-tight containers, in an inert atmosphere, away from moisture. Schlenk flasks are good storage containers.

Disposal

Lithium hydride can be safely neutralized by slowly adding it in a large volume of alcohol, followed by slow addition of water.

References

1. ↑ Brandt, P.; Acta Chemica Scandinavica (1947-1973); vol. 3; (1949); p. 1050 - 1057
2. ↑ Gilman, H.; Jacoby, A. L.; Ludeman, H.; Journal of the American Chemical Society; vol. 60; (1938); p. 2336 - 2338

Relevant Sciencemadness threads

• Lithium hydride
• Lithium Hydride synthesis
• Lithium Hydride Preperation
• LiH Production Apparatus Design and Operation