An aqueous solution containing $0.122\; g$ of unknown compound $S$ has a volume of $100\; mL$ and an osmotic pressure of $16.0\;torr$ at $20.0 ^ oC.$ Calculate the molar mass of the compound.
$\pi=\frac{16.0}{760}atm$ $[S]=\frac{\pi}{RT}=\frac{\frac{16.0}{760}}{0.082\cdot 293}=8.77\cdot 10^{-4}\frac{mol}{L}$ $n_S=[S]\cdot V= 8.77\cdot 10^{-4}0.1=8.77\cdot 10^{-5}mol$ $M_S=\frac{m_S}{n_S}=\frac{0.122}{8.77\cdot 10^{-5}}=1.39\cdot 10^3\frac{g}{mol}$
