State as to why
(a) a solution of `Na_(2)CO_(3)` is alkaline ?
(b) alkali metals are prepared by electrolysis of their fused chlorides?
(c) sodium is found to be more useful than potassium ?

Explanation

Sodium carbonate being a salt of strong base (NaOH) and weak `(H_(2)CO_(3))`, forms an alkaline solution upon hydrolysis
`Na_CO_(3)+2H_(2)Otounderset(("Strong base"))(2NaOH)+underset(("Weak acid"))(H_(2)CO_(3)`
(b) Since alkali metals are highly reactive chemically,the react with water to evolve hydrogen gas. These are therefore, prepared by the electrolysis of their fused chlorides.
Sodium is relatively more abundant than potassium. At the same time, it is also less reactive and its reactions with other substances can be better controlled.