A gas bottle contains a mixture of Helium and Oxygen molecules (O2 is diatomic). The root-mean-square velocity for the O2 molecules is 482 m/s. Find vrms for the Helium atoms.
and solve for velocity of He, however, i am not sure what numbers to plug in for the mass.
The Attempt at a Solution
I filled everything in but the masses, I know that oxygen is diatomic, or O2, but what does that mean I put in for the mass? Do I need to use the mass numbers by looking at a periodic table?