where \(w_{1}, \,M_{1}=\) mass in \(g\)
and mol. mass of solvent
\(w_{2}, M_{2}=\) mass in \(g\)
and mol. mass of solute
Let \(M_{2}=x\)
\(P^{o}=185\,torr\) ; \(P_{s}=183\,torr\)
\(\frac{185-183}{183}=\frac{1.2 \times 58}{100 x}\)
(Mol. mass of acetone \(=58\) )
\(x=64\)
Molar mass of substance \(=64\)