Question

Write the reaction for preparation of lithium aluminium hydride and give it’s uses

Answer 1

Explanation:

Preparation-

Lithium aluminum hydride is prepared on small scales by reacting lithium hydride with aluminum chloride:

4 LiH + AlCl3 → LiAlH4 + 3 LiCl

Industrial Preparation-

In the first step, sodium aluminum hydride is formed by reacting sodium and aluminum metals with hydrogen under high pressure and temperature. In the second step, this product is reacted with LiCl, to exchange the metal cations (Na for Li) giving the final LAH product:

1- Na + Al + 2 H2 → NaAlH4

2- NaAlH4 + LiCl → LiAlH4 + NaCl

Uses-

It is mainly used as a reducing agent in organic synthesis, and a reagent in the preparation of a variety of pharmaceuticals, organic chemicals and metal hydrides (such as NaH). It is also used as a polymerization catalyst and a propellant. It is considered as a potential hydrogen storage agent in fuel cells.