Is the molar mass of oxygen 16 or 32?

Oxygen Atom ##~~ 16## Oxygen Gas (that we inhale) ##~~32##

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 (##mass_O ~~ 16##). However since oxygen rarely exists as purely a single atom, we say that the molar mass of oxygen is 32 or ##mass_(O_2) = 32 g/(mol)##.

Now when computing for empirical formula sample problems, use ##16 g/(mol)## 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 you need to compute for.