# What is the empirical formula of a compound that contains 30.4% nitrogen and 69.6% oxygen by mass?

May 27, 2017

$N {O}_{2}$..........

#### Explanation:

AS is typical in these problems, we ASSUME an $100 \cdot g$ mass of unknown compound, and we divide thru by the atomic mass:

$\text{Moles of nitrogen} = \frac{30.4 \cdot g}{14.01 \cdot g \cdot m o {l}^{-} 1} = 2.17 \cdot m o l .$

$\text{Moles of oxygen} = \frac{69.6 \cdot g}{15.999 \cdot g \cdot m o {l}^{-} 1} = 4.35 \cdot m o l .$

And we divide thru by the SMALLEST molar quantity to get an empirical formula of $N {O}_{2}$...........