# The molar mass of barium nitrate (Ba(NO_3)_2) is 261.35 g/mol. What is the mass of 5.30 x 10^22 formula units of Ba(NO_3)_2?

Well, how many barium nitrate formula units are in $261.35 \cdot g$?
It is fact that $6.023 \times {10}^{23}$ formula units of barium nitrate have a mass of $261.35 \cdot g$. This is what we specify when we say molar mass. And thus the mass of $5.30 \times {10}^{22}$ formula units of barium nitrate is the quotient multiplied by the molar mass:
$\frac{5.30 \times {10}^{22}}{6.023 \times {10}^{23}} m o l \times 261.35 \cdot g \cdot m o {l}^{-} 1$ =??g