How Does the Concentration Ratio of Nitrogen to Hydrogen Change with Altitude?

[jaumzaum]

I was trying to solve a problem from Irodov book that asked how the concentration ratio of nytrogen and hydrogen varies with the altitude (initial ratio = n0), considering the temperature to be constant.

If there was only one gas,

http://img543.imageshack.us/img543/664/77110068.png

dP = -dm g/A
dP = -dV ρ g/A
dP = -dh ρ g
dP = -dh PMg/RT
dP/P = -Mg/RT dh
P = P₀e^-hMg/RT

Where:
P₀ is initial pressure
M is molar mass
ρ is density

But how would it work for 2 different gases?

 

[haruspex]

Dalton's Law? Could it be that simple?

 

[jaumzaum]

Dalton's Law? Could it be that simple?

Thanks haruspex, I had completely forgot the Dalton's Law :'(
Don't know where my head was