`M_(B)-(K_(f)xxW_(B))/(DeltaT_(f)xxW_(A))`
Mass of non-electrolyte`(W_(B))=10 g`
Mass of benzene `(W_(A))=50 g=0.005 Kg`.
Depression in freezing point `(DeltaT_(P))=0.40 K`
Molal depresion constant`(K_(f))=5.12 K kg mo^(-1)`
`T_(f)=((5.12 K kg mol^(-1))xx(1.0 g))/((0.40 K)xx(0.005 kg))=256 g mol^(-1)`