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

(b) The discharge potentials of alkali metals are much higher than that of hydrogen and therefore, when the aqueous solutions of alkali metal chlorides are subjected to electrolysis, `H_2` is evolved preferably than the alkali metal at the cathode. Therefore, to prepare alkali metals, electrolysis of their fused chlorides is carried out.
(c) Sodium ions are found primarily in the blood plasma and in the interstitial fluid which surrounds the cells. On the other hand, potassium ions are present within the cell fluids. Sodium ions help in the transmission of nerve signals, regulating the flow of water across cell membranes and in the transport of sugars and amino acids in the cells. Thus, sodium is more useful than potassium.