Chemistry Forum

Given Methane's molecular structure of CH₄ (one carbon atom bonded to four hydrogen atoms) and Oxygen is O₂ (two oxygen atoms bonded together), and given that the atomic weight of Methane should be 16.05g/mol (1xC [12.01g/mol] + 4xH [1.01g/mol]) while the atomic weight of Oxygen should be 31.998g/mol (2xO [15.999g/mol]). In a laboratory environment should Methane rise above Oxygen when both gases are placed in a container like a flask or test-tube, if the temperature and pressure were not a factor?

Correct. Check specific gravity. CH₄ 0.657 kg/m^3 and O₂ 1,43 kg/ m^3.

Thanks

So, conversely Carbon Dioxide's molecular structure of CO₂ (one carbon atom bonded to two oxygen atoms) and Oxygen is O₂ (two oxygen atoms bonded together), and given that the atomic weight of Carbon Dioxide should be 44.009g/mol (1xC [12.01g/mol] + 2xO [15.999g/mol]) while the atomic weight of Oxygen is 31.998g/mol (2xO [15.999g/mol]). In a laboratory environment should Carbon Dioxide fall below Oxygen when both gases are placed in a container like a flask or test-tube, if the temperature and pressure were not a factor?

If that is correct, what factors (I'm assuming it is Temperature & Pressure, possibly caused by density), causes Carbon Dioxide' to rise above (become lighter) than Oxygen in a flask or test tube?

Why it should be lighter. Same before specific gravity is 1,98 kg/m^3 for CO₂.
Already given CH₄ 0.657 kg/m^3 and O₂ 1,43 kg/ m^3.

But gases are not liquids. They mix together each other, like air a mixture off several gases like nitrogen, oxygen, carbondioxide, noble gases, etc.

Thanks again ChenBeier,

Re. "But gases are not liquids. They mix together each other, like air..."; Okay, but in a Test Tube or Flask, as previously suggested, would one gas that had a high specific gravity weight sit at the bottom of said Test Tube, if the Test Tube wasn't disturbed in any way?

I'm thinking of situations where clouds or plumes of certain gases can be seen to sit at distances above the ground, or how air pollution rises up and sits above some cities. I'm also recalling some basic experiments I carried out in a lab many years ago where a reaction released a gas that appeared to fill a Test Tube from the bottom, pushing another coloured gas up out of the tube. These events indicate that not all gases mix and that a gas with a high specific gravity weight would displace gases of a lighter specific gravity weight form the lowest point, if left undisturbed. Without getting into the areas of thermodynamics and gas dispersion, are the basics of what I've suggested correct?

Yes I told already.

Already discussed above.

jesse99 wrote: ↑Fri Jul 04, 2025 8:29 pm Yes, methane (CH₄) is lighter than oxygen (O₂ Poor Bunny ), with a molar mass of about 16 g/mol compared to oxygen’s ~32 g/mol. So, in a still environment without external forces or mixing, methane would naturally rise above oxygen due to its lower density.

Thanks!