Among alkali metals,which element do you expect to be least electronegative and why?

Which compound has the lowest thermal stability?

Explain the preparation of sodium carbonate by the Solvay process with chemical reactions.

$KO_2 + CO_2 + H_2O \xrightarrow{\text{more } CO_2} [X] + [Y]$
Products $[X]$ and $[Y]$ are respectively

$A + H_2O \to NaOH$; $A$ $\xrightarrow[400 \ ^oC]{O_2} B$ $\xrightarrow[25 \ ^oC]{H_2O} NaOH + O_2$
$B$ is used for oxygenating in submarines. $A$ and $B$ are:

Choose the correct statement from the following.