Question

3 Consider three 1-L flasks at the same temperature and pressure:Flask A contains CO gas, flask B contains N2 gas, and flask C contains O2 gas. Which contains the lowest density?

(A)flask A (B)flask B (C)flask C D)All are the same (E)Two of the flasks contain gases at the same density

Answer 1

Well, flask A and flask B contain a gas of equivalent densities.....

Explanation:

We assume ideality and solve for density in the `"Old Ideal Gas equation"`...

`PV=nRT`, and thus `n/V=P/(RT)`

But `n="Mass"/"Molar mass"`

And so `("Mass"/"Molar mass")/V=P/(RT)`...

And so...`underbrace("Mass"/V)_("i.e. density, "rho)=P/(RT)xx"molar mass"`

And so...`rho=P/(RT)xx"molar mass"`

And thus the LEAST density will result from the gas with the LEAST molecular mass..... And to a first approx. the densities of A and B will be equal and less than that exerted in C by dioxygen...a heavier gas...i.e. `32.0*g*mol^-1` versus `28.0*g*mol^-1`...