Question #98436

Feb 5, 2016

Oxygen Atom $\approx 16$
Oxygen Gas (that we inhale) $\approx 32$

Explanation:

This question is quite confusing considering that we tend to refer to oxygen (the element with symbol O) and to the oxygen (the gas we inhale ${O}_{2}$) using the same term.

Since oxygen the element consist only of 1 atom of Oxygen, then we will use the atomic weight of oxygen for this mass ($m a s {s}_{O} \approx 16$). However since oxygen rarely exists as purely a single atom, we say that the molar mass of oxygen is 32 or $m a s {s}_{{O}_{2}} = 32 \frac{g}{m o l}$.

Now when computing for empirical formula sample problems, use $16 \frac{g}{m o l}$ since it corresponds to the mass of 1 atom of oxygen. Just remember to multiply the value to the subscript of Oxygen when you need to determine the molar masses of the compounds you need to compute for.