Question:
How can saline hydrides remove traces of water from organic compounds?
Solution:
Saline hydrides are ionic in nature. They react with water to form a metal hydroxide along with the liberation of hydrogen gas. The reaction of saline hydrides with water can be represented as:
$\mathrm{AH}_{(s)}+\mathrm{H}_{2} \mathrm{O}_{(n)} \longrightarrow \mathrm{AOH}_{(a q)}+\mathrm{H}_{2(g)}$
(where, A = Na, Ca,……)
When added to an organic solvent, they react with water present in it. Hydrogen escapes into the atmosphere leaving behind the metallic hydroxide. The dry organic solvent distills over.