How many moles of $Mg_3(PO_4)_2$ will contain $0.50 \ mol$ of oxygen atoms?

How many water molecules are there in one drop of water $($Volume $= 0.0018 \ mL)$ at room temperature?

In a flask, the weight ratio of $CH_{4(g)}$ and $SO_{2(g)}$ at $298 \ K$ and $1 \ bar$ is $1:2$. The ratio of the number of molecules of $SO_{2(g)}$ and $CH_{4(g)}$ is

The number of moles of $SO_2Cl_2$ in $13.5 \ g$ is

How many oxygen atoms are present in $4.4 \ g$ of $CO_2$?

The number of atoms present in $0.1 \ mol$ of a triatomic gas is: $(N_A = 6.022 \times 10^{23} \ mol^{-1})$