1. The problem statement, all variables and given/known data At a certain temperature a sample of oxygen has a pressure of 2.0 x 10^6 Pa, and a density of 4.0 x 10^-3 g cm^-3. Find the average speed of the oxygen molecules of the gas. 2. Relevant equations Ek= 3/2kT Ek= 1/2mv^2 3. The attempt at a solution I know that the mass of oxygen is 32 g per mole so with this i could find the mass of an individual molecule= 32 g/ 6.02 x 10^23 g =5.3 x 10^-26 kg I know P= 2.0 x 10^6 Pa I just dont understand what to do with the density? can somebody please help me, any help would be much aprpeciated:) Thankyou!