Question

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

• A. Their nitrates decompose on heating to give the corresponding nitrites and oxygen
• B. Their chlorides are deliquescent and crystallise as hydrates
• C. They react with water to form hydroxide and hydrogen
• D. They readily react with halogens to form ionic halides, $M^{+}{X}^{-}$

Answer 1

The correct option is C They react with water to form hydroxide and hydrogen

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 $Cs$)
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
Hence only option (c) is true for all the alkali metals.