Which of the following metals is not found in the free state?

Assertion $(A)$: $K$, $Rb$, and $Cs$ form superoxides.
Reason $(R)$: The stability of the superoxides increases from $K$ to $Cs$ due to the decrease in lattice energy.
The correct answer is:

In which of the following reactions is hydrogen gas not liberated?

Nitre is

Which of the following reactions is correct for the thermal decomposition of lithium nitrate?

$Al +$ aq. $NaOH$ (excess) $\longrightarrow P + Q$. $P$ and $Q$ are