Give uses of $sodium$ $hydrogen$ $carbonate$.

The electronic configuration of $Cs$ is

The strongest reducing agent among the following is:

Which of the following ions forms a highly soluble hydroxide in water?

Why is $Li_{2}CO_{3}$ decomposed at a lower temperature whereas $Na_{2}CO_{3}$ at higher temperature?

The correct statements are:
$I$. The low solubility of $LiF$ is due to its high lattice enthalpy.
$II$. $LiBr$ is soluble in acetone.
$III$. $LiCl$ is soluble in pyridine.
$IV$. The order of melting points of alkali metal halides is $MF > MCl > MBr > MI$.