Reactions of Lithium Hydride

Lithium hydride(LiH）powder reacts rapidly with air of low humidity, forming LiOH, Li2O and Li2CO3. In moist air the powder ignites spontaneously, forming a mixture of products including some nitrogenous compounds. The lump material reacts with humid air forming a superficial coating which is a viscous fluid. This inhibits further reaction, although the appearance of a film of 'tarnish' is quite evident. Little or no nitride is formed on exposure to humid air. The lump material, contained in a metal dish, may be heated in air to slightly below 200 °C, without igniting, although it ignites readily when touched by an open flame. The surface condition of LiH, presence of oxides on the metal dish, etc., have a considerable effect on the ignition temperature. Dry oxygen does not react with crystalline LiH unless heated strongly, when an almost explosive combustion occurs.

LiH is highly reactive toward water and other protic reagents:
LiH + H2O → LiOH + H2
LiH is less reactive with water than Li and thus is a much less powerful reducing agent for water, alcohols, and other media containing reducible solutes. This is true of all the binary saline hydrides.
LiH pellets slowly expand in moist air forming LiOH; however, the expansion rate is below 10% within 24 hours in a pressure of 2 mm of water vapor. If most air contains carbon dioxide then the product is lithium carbonate. LiH reacts with ammonia, slowly at room temperature, but the reaction accelerates significantly above 300 °C. LiH reacts slowly with higher alcohols and phenols but vigorously with lower alcohols.
LiH reacts with sulfur dioxide:
2 LiH + 2 SO2 → Li2S2O4 + H2
though above 50 °C the product is lithium sulfide.
LiH reacts with acetylene to form lithium carbide and hydrogen. With anhydrous organic acids, phenols and acid anhydrides LiH reacts slowly producing hydrogen gas and the lithium salt of the acid. With water-containing acids, LiH reacts faster than with water. Many reactions of LiH with oxygen-containing species yield LiOH which in turn irreversibly reacts with LiH at temperatures above 300 °C:
LiH + LiOH → Li2O + H2
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