State as to why:
$(a)$ a solution of $Na_2CO_3$ is alkaline?
$(b)$ alkali metals are prepared by electrolysis of their fused chlorides?
$(c)$ sodium is found to be more useful than potassium?

(A) When $Na_2CO_3$ is added to water,it undergoes hydrolysis to produce $NaHCO_3$ and $NaOH$. Since $NaOH$ is a strong base,the resulting solution becomes alkaline.
$Na_2CO_3 + H_2O \rightarrow NaHCO_3 + NaOH$
$(b)$ Alkali metals are strong reducing agents and highly electropositive,making their extraction by chemical reduction of oxides or displacement reactions impossible. Electrolysis of aqueous solutions is also not feasible because the liberated metals react with water. Therefore,they are prepared by the electrolysis of their fused chlorides.
$(c)$ $Na^+$ ions are primarily found in blood plasma and interstitial fluids,where they regulate nerve signal transmission,water flow across cell membranes,and the transport of sugars and amino acids. While $K^+$ ions are essential within cells,$Na^+$ ions perform these critical extracellular functions,making them highly significant.