Question
The alkali metals form salt like hydrides by the direct synthesis at elevated temperature.
The thermal stability of these hydrides decreases in which of the following orders ?
A.
$$CsH > RbH > KH > NaH > LiH$$
B.
$$KH > NaH > LiH > CsH > RbH$$
C.
$$NaH > LiH > KH > RbH > CsH$$
D.
$$LiH > NaH > KH > RbH > CsH$$
Answer :
$$LiH > NaH > KH > RbH > CsH$$
Solution :
As the size of the alkali metal cation increases, thermal stability of their hydrides decreases.
Hence, the correct order of thermal stability of alkali metal hydrides is $$LiH > NaH > KH > RbH > CsH$$