\(w _{solvent}=75 g\quad\quad\) \(M =\) Mol . Wt .of solute
\(T _{ B }^{\prime}=373.535\, K\)
\(T _{ B }^{o}=373.15\, K\)
\(\Delta T _{ B }=0.385= K _{ b } \text { molality }\)
\(0.385=0.52 \times\left(\frac{2.5}{ M } \times \frac{1000}{75}\right)\)
\(M =45 \,g\, mol ^{-1}\)