Hello. First post on the forum.
I'm an undergrad in Chemistry here in Brazil (1st year), and I've been challenged by my veterans (talk about peer pressure) to solve a chemistry problem:
"There's a gaseous mixture of Ethane
filled inside a 200cm³
flask, at 750mmHg
. If the mass of the gas in the flask is 0,384g
, what is the molar fraction of the Butane in the flask?"
I've been trying to solve this for about 2 hours now. Since they are gases, the same volume has the same amount of moles as long as temperature and pressure are kept constant, but I can't find how many moles that is, because I don't have the molar fraction of the gases (which is the solution to the problem itself).
I would be thankful if someone could shed me some light here, but please don't give it away at once, for I wanna try and solve it myself, as otherwise I would have no bragging rights when I DO get it, right?
Using p = PM/RT (Ideal Gas Density), I got the densities for both gases under the specified conditions, though they seem to be useless, since they are overshooting the overall mixture's mass by a lot, probably due to the big difference between ethane/butane and an ideal gas.
Dbutane = 0.0235 kg/L = 0.0235 g/mL
Dethane = 0.0121 kg/L = 0.0121 g/mL