Under identical conditions of temperature and pressure, which of the following gasses is the lightest? a) #"Ne"# b) #"O"_2# c) #"Ar"# d) #"H"_2#

1 Answer
Apr 9, 2018

Well, which one contains the least mass per particle?


The lightest gas just has the least mass.

But under the same temperature and pressure, all four gases (assuming ideality) have the same molar volume #barV -= V//n#. Hence, in the same container, there contains the same number of mols of each gas.

Therefore, since higher molar mass gives more mass for the same number of mols, the lightest gas has the smallest molar mass.