[LeNabot1987]

Hello Chemical Forums!

I'm doing exercices to get a feel of pV=nRT, and there was this one I couldn't find the solution to this:

Give the concentration, c, in mol/dm³ of a solution of an ideal gas in water that has the same average distance between its molecules as in the pure gas at T=273K, and at p=100Pa.

I know that means the quantity of matter in the solution (n for the gas and n' for the water) and in the gas (n") for the same volume, V, must be the same, so n+n'=n" and n"=pV/RT from the formula, so:

n+n'=pV/RT
n/V=p/RT-n'/V
c=p/RT-n'/V

But then I'm stuck to find what n'/V could be, since we know nothing about the solution's temperature or pressure. Any ideas?

[LeNabot1987]

Nevermind. The question isn't really clear. Actually n=n" so n/V=p/RT and c=4.41e-5 mol/dm³.