An ionic hydride of an alkali metal has significant covalent character and is almost unreactive towards oxygen and chlorine . This is used in the synthesisi of other useful hydrides. Write the formula of this is used in the synthesis of other hydrides. Write the formula of this hydride. Write its reaction with `Al_(2)Cl_(6)`.

Explanation

The alkali metal hydride with significant covalent character is lithium hydride (LiH). Actually ionisation enthalpy of lithium is quite high `(Delta_(i)H_(1)=520kJ mol^(-1))` and its size is also small (atomic radius=123Å). Its compounds are generally covalent in nature.
`8LiH(s)+Al_(2)Cl_(6)(aq) to underset("Lithium aluminium hydride")(2LiAlH_(4)(aq)+6LiCl(s))`