We solve for $n$ and $n="Mass"/"Molar mass"$ $=$ $(PV)/(RT)$
And, $"Molar mass"$ $=$ $(RTxx"mass")/(PV)$
$=$ $(RT)/Pxx"mass"/V$
$=$ $(rhoRT)/P$ because $"mass"/V=rho="density"$
And thus,
$"Molar mass"$ $=$ $(rhoRT)/P$
$(1.88*g*cancel(L^-1)xx0.0821*cancel(L)*cancel(atm)*cancel(K^-1)*mol^-1xx273.15*cancel(K))/(1.00*cancel(atm))$
Well, this gives me an answer in $g*mol^-1$, so I might be doing something right.
I get (finally!), $"Molar mass"$ $=$ $42.2*g*mol^-1$
Now the molecular formula is always a mulitiple of the empirical formula, of course, the multiple might be $1$.
$("Empirical formula")xxn="Molecular formula"$
And $nxx(2xx1.00794 +12.01)*g*mol^-1=42.2*g*mol^-1$.
Clearly, $n=3$, and molecular formula $=$ $C_3H_6$. We have $"propylene"$ or $"cyclopropene"$.
This is a first year problem, I take it. I ask because it gives me an idea as to how to bowl.
