Caesium is used in

When $Na$ is heated at $300\,^oC$,it forms $X$. It absorbs $CO_2$ to form $Na_2CO_3$ and $Y$. What is $Y$?

Lead pipes are not used for carrying drinking water because:

$STATEMENT-1$: Alkali metals dissolve in liquid ammonia to give a blue solution because
$STATEMENT-2$: Alkali metals in liquid ammonia give solvated species of the type $[M(NH_3)_n]^{+}$ ($M=$ alkali metals).

Which of the following statements is false for alkali metals?

Which of the following metals,upon burning in moist air,does not produce the smell of ammonia?