Question

rank the gases Ar, N2,CH4, and C2H6 in order of the increasing density at STP
answer: CH4<N2<C2H6<Ar
please help me solve this

Answer 1

at stp, one mole of each occupies the same volume, so density then in the same order as mole mass.

If you want to work it out at stp,
density CH4=molemassCH4/22.4liters
density N2=molemass N2/22.4 liters

and so one.