Answer
See the answer below.
Work Step by Step
Osmotic pressure: $\Pi=cRT\rightarrow c=(3.17/760)\ atm\div(0.082\ mol.L/atm.K\times 298\ K)=1.707\times10^{-4}\ mol/L$
Number of moles: $1.707\times10^{-4}\ mol/L\times 0.1\ L=1.707\times10^{-5}\ mol$
Molar mass: $5.00\times10^{-3}\ g\div1.707\times10^{-5}\ mol=292.92\ g/mol$
In one mol of this substance:
$n_C\times12.01/292.92=73.94/100\rightarrow n_H=18.03\approx18$
$n_H\times1.01/292.92=8.27/100\rightarrow n_H=23.98\approx24$
$n_{Cr}\times52.00/292.92=17.19/100\rightarrow n_{Cr}=1.00\approx1$
Empirical and molecular formula of the compound: $C_{18}H_{24}Cr$
