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

$7.0 \, g$ of $N_2$,$8.0 \, g$ of $O_2$,and $34.0 \, g$ of $NH_3$ are present in a $1 \, L$ vessel. The active masses in $mol \, L^{-1}$ are respectively:

How many moles of water are present in $180 \ g$ of water?

The ratio of the number of oxygen atoms $(O)$ in $16.0 \ g$ ozone $(O_3)$,$28.0 \ g$ carbon monoxide $(CO)$,and $16.0 \ g$ oxygen $(O_2)$ is (Atomic mass: $C = 12$,$O = 16$ and Avogadro's constant $N_A = 6.0 \times 10^{23} \ mol^{-1}$)

What does $1 \text{ mole}$ of $CO_2$ contain?

Find the number of electrons present in $34 \ g$ of $NH_{3(g)}$. (Express your answer in terms of $N_A$)