$A$ mixture of lime paste is composed of sand,water,and which of the following?

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?

The lightest metal is

$KO_2$ (Potassium superoxide) is used in confined spaces and submarines because it

Sodium oxide dissolves in water to give sodium hydroxide,which indicates its:

What happens when : $(i)$ sodium metal is dropped in water? $(ii)$ sodium metal is heated in free supply of air? $(iii)$ sodium peroxide dissolves in water?