J.R. S. answered • 04/14/19

Ph.D. University Professor with 10+ years Tutoring Experience

Density is given as mass/volume for a gas, it will depend on the pressure and temperature.

If we assume STP where T = 273K and P = 1 atm, we can calculate the volume given the moles of gas.

If you had 100 g of gas...

21% O2 = 21 g O2 x 1 mol/32 g = 0.66 moles O2

70% N2 = 79 g N2 x 1 mol/28 g = 2.82 moles N2

Total moles of gas = 3.48 moles

PV = nRT

V = nRT/P = (3.48)(0.0821)(273)/1 = 78 liters = 78,000 mls

density = mass/volume = 100 g/78,000 ml = 0.00128 g/ml = 1.28 g/L etc....

J.R. S.

04/14/19

Farah H.

Ah Thank you! I very much appreciate the time you took to answer!04/14/19