Question

Which of the following statements is true for all the alkali metals ?

Answer 1

1) $4LiN{O}_3\to 2L{i}_{2}O+4N{O}_2+O_2$
$2NaN{O}_3\to 2NaN{O}_2+O_2$ (similar decomposition with the nitrates of $K,Rb$ and $Cs$)
From the above reaction it is clear that lithium nitrate produces lithium oxide and oxygen on decomposition while sodium nitrate produces sodium nitrite and oxygen Hence option 'a' is wrong.

2) Only $LiCl$ is deliquescent and crystallises as a hydrate $LiCl.2H_{2}O$.

3) All alkali metal will react with water, liberating hydrogen and forming respective hydroxides.
$2M+2H_{2}O\to 2M^{+}+2O{H}^{-}+H_2$ (M = an alkali metal)

4) Halides of $Li$ are covalent in nature so option 'd' is wrong.
Hence option (c) is true for all the alkali metals.