State as to why

(a) a solution of Na₂CO₃is alkaline ?

(b) alkali metals are prepared by electrolysis of their fused chlorides ?

(c) sodium is found to be more useful than potassium ?

(a) When sodium carbonate is added to water, it hydrolyses to give sodium bicarbonate and sodium hydroxide (a strong base). As a result, the solution becomes alkaline.

(b) It is not possible to prepare alkali metals by the chemical reduction of their oxides as they themselves are very strong reducing agents. They cannot be prepared by displacement reactions either (wherein one element is displaced by another). This is because these elements are highly electropositive. Neither can electrolysis of aqueous solutions be used to extract these elements. This is because the liberated metals react with water.

Hence, to overcome these difficulties, alkali metals are usually prepared by the electrolysis of their fused chlorides.

(c) Blood plasma and the interstitial fluids surrounding the cells are the regions where sodium ions are primarily found. Potassium ions are located within the cell fluids. Sodium ions are involved in the transmission of nerve signals, in regulating the flow of water across the cell membranes, and in transporting sugars and amino acids into the cells. Hence, sodium is found to be more useful than potassium.

Ans (a)Sodium carbonate is a salt of a strong base and a weak acid. When dissolved in water, since carbonic acid is weak, it has a low pKa. This makes the H3O+ from water to be removed from the solution to form HCO3-, leaving an excess of OH- in the solution, thus making the solution alkaline.
Ans (b) Alkali metals cannot be obtained by the electrolysis of the aqueous solution of their salts because H2 is liberated at cathode instead of alkali metal. That’s why alkali metals are prepared by electrolysis of their fused chloride.
Ans(c)Sodium is used in seasoning the meats and is a part of the human diet.