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Lithium Hydride

Lithium hydride, represented by the chemical formula LiH, is a crystalline or powdery inorganic compound [1]. The alkali metal hydride has a molecular mass less than 8 and is the lightest ionic compound [1, 2].

Lithium Hydride Identification

CAS Number 7580-67-8 [1]
PubChem CID 62714 [1]
ChemSpider ID 56460 [3]
UN Number 1414 [1]
ICSC Number 0813 [1]
EC Number 231-484-3 [1, 4]
RTECS Number OJ6300000 [1]
InChI Key SRTHRWZAMDZJOS-UHFFFAOYSA-N [1]

Lithium Hydride

How to make Lithium Hydride

LiH can be synthesized by the reaction of solid lithium with hydrogen gas, which is represented by the following chemical equation [5]:

2Li + H2 → 2LiH

The reaction occurs rapidly at temperatures over 600 °C, and the yield is increased to 98% [5]. It can also occur at 29 °C, but the yield is much lower [5].

Lithium hydride is also produced by combining lithium aluminum hydride and sodium hydroxide through metathesis in tetrahydrofuran (THF) [6]:

LiAlH4 + NaH → NaAlH4 + LiH

Reactions with Other Compounds

LiH reacts with air to produce Li2O, LiOH, and Li2CO3, while it forms nitrogenous compounds in moist air [5]. It spontaneously undergoes a chemical reaction with water which is given as follows [5]:

LiH + H2O → Li+ + H2 + OH

Lithium hydride reacts with sulfur dioxide to form lithium dithionite at a temperature above 50 °C [5]:

2LiH + 2SO2 → Li2S2O4 + H2

When it reacts with acetylene, it produces hydrogen and lithium carbide [5]:

LiH + LiOH →Li2O + H2

Properties and Characteristics of Lithium Hydride

General Properties

Molar Mass/Molecular Weight 7.948 g/mol [1]

Physical Properties

Color and Appearance Off-white, gray, or translucent; light bluish-gray lumps in commercial product [1]
Odor Odorless [1]
Melting Point 680 °C, 1256 °F [1]
Boiling Point 900-1000 °C, 1650-1830 °F (decomposes) [1]
Density 0.76-0.8 g cm-3 [1]
State of matter at room temperature Solid [1, 4]
Solubility Somewhat soluble in dimethylformamide; it reacts with diethyl ether, ammonia, and ethanol
Solubility in Water Reacts [1]
Magnetic Susceptibility (χ) -4.6 X 10-6 cm3/mol
Heat Capacity (C) 3.51 J/(g.K)

Atomic Properties

Crystal Structure Octahedral cubic (NaCl-type) [7]

Lithium Hydride Structure

What is It Used for

  • Synthesis of hydrogen because LiH has the highest H2 content of any hydride [4]
  • Manufacturing catalysts used for polyolefin plastics [8]
  • Missiles, aircraft, and rocket fuel [8]
  • Degasification, deoxidization, and desulfurization in the metallurgical industry [8]
  • Forming alloys with magnesium and aluminum for aerospace use [8]
  • Shielding and absorbing neutrons in mobile nuclear reactors, used along with lithium-7 [9]

Is It Toxic

Repeated contact or overexposure can cause acute irritation of skin, mucous membranes, and eyes [1]. When burned, it forms irritating alkali fumes [1]. LiH forms dust clouds that may explode when they come in contact with heat, flame, or oxidizing materials [1].

References

  1. Lithium Hydride – Pubchem.ncbi.nlm.nih.gov
  2. Lithium Hydride – Chem.libretexts.org
  3. Lithium Hydride – Chemspider.com
  4. Lithium Hydride – Americanelements.com
  5. Technical Memorandum Compilation Of The Properties Of Lithium Hydride – Ntrs.nasa.gov
  6. Lithium Aluminium Hydride – Cs.Mcgill.ca
  7. Lithium Hydride – Webelements.com
  8. Lithium Hydride – Toxnet.nlm.nih.gov
  9. Lithium Hydride – A Space Age Shielding Material – Ntrs.nasa.gov

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