The mass of $112 \ cm^3$ of $CH_4$ gas at $STP$ is ............. $g$.

What is the number of moles of nitrogen atoms present in one mole of cytosine?

Avogadro number is

Calculate the number of $Ca^{2+}$ ions in $222 \ g$ of anhydrous calcium chloride $(CaCl_2)$? (Atomic mass: $Ca = 40 \ u$,$Cl = 35.5 \ u$)

Two flasks $A$ and $B$ of $500 \ mL$ each are filled with $O_2$ and $SO_2$ respectively at $300 \ K$ and $1 \ atm$ pressure. Then the flasks contain:

$4.4 \ g$ of $CO_2$ and $2.24 \ L$ of $H_2$ at $\text{STP}$ are mixed in a container. The total number of molecules present in the container will be :