Question
The density of a mixture of Nitrogen and Oxygen is $\pu{4.7 g L-1}$. Its given that $P = \pu{4 atm}$, and that $T = \pu{298 K}$. Assuming both gasses are ideal gasses, what is the molar fraction of nitrogen in this mixture?
Answer
Mole fraction of nitrogen is 0.82.
My Attempt
I tried using the $PV=nRT$ equation, having $V = 1$ and $n$ being the number of moles of both gasses together.
Then I used a second equation for the density being $D=\dfrac{16n_1+14n_2}{V}$. However I got a negative answer that is also larger than $1$.