What else is present in a fire extinguisher along with ${H_2}SO_4$?

$KO_2$ (potassium superoxide) is used in oxygen cylinders in space and submarines because it

Which hydride is most stable?

$Na$ and $Li$ are placed in dry air. We get

Arrange the following compounds in the increasing order of their thermal stability. Identify the correct sequence.
$I - K_2CO_3, II - MgCO_3, III - CaCO_3, IV - BeCO_3$

Sodium metal reacts with $Al_2O_3$ at high temperature to give a sodium compound $X$. Compound $X$ reacts with carbon dioxide in water to give $Y$. What is $Y$?