Question

A mixture of Ar and N2 gases has a density of 1.487g/L at STP. What is the mole fraction of each gas?

Answer 1

You can do this using a bit of algebra. If the mole fraction of Ar is x, then the mole fraction of N2 is 1-x. The density of Ar on its own is 1.784 g/L, and the density of N2 on its own is 1.251 g/L (already this is looking good because the density of the mixture is between the densities of each pure substance).

We can find the density of the mixture by adding together the densities of each pure substance multiplied by the mole fraction of each pure substance:

\[1.487=1.784x+1.251(1-x)\]
Solve for x and you'll have your answers!

Answer 2

How did you figure out the densities of Ar and H2

Answer 3

Google :P

Answer 4

Densities are an empirically (experimentally) determined property to my knowledge

Answer 5

say this was given on a test and google couldn't be used

Answer 6

You would be given the densities on a test. Unless it was some special case but even in that special case you would be given enough information to find the density.

Answer 7

No teacher/prof is going to make you memorize densities, besides maybe the density of water which is roughly 1kg/m^3 or 1g/mL at STP

Answer 8

^

Answer 9

if you weren't given the densities or couldn't look them up, you'd use the ideal gas law to find the density of pure Ar and pure N2, and there you are