Rank the following gases in order of heaviest to lightest molar mass. ||| A Chlorine B Xenon C Carbon monoxide D Hydrogen sulfide?

Got a Periodic Table? You simply have to add up the appropriate masses.

The one trick in this question is the molecular weight of chlorine gas. Save for the Noble Gases, ALL the elemental gases are bimolecular: ##H_2##, ##N_2##, ##O_2##, ##F_2##, ##Cl_2## (in fact all the halogens are bimolecular in the elemental state, gas, solid, or liquid).

So I suspect the lightest gas will be carbon monoxide, and the heaviest gas xenon. But please make sure I am right!