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On dissolving 0.25 g of a non-volatile substance in 30 mL of benzene (density 0.8 g mL^(-1)), its freezing point decreases by 0.40^(@)C. Calculate the molecular mass of the non-volatile substance. K_(f) for benzene is 5.12 Km^(-1) . |
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Answer» `K_(f)=5.12" K kg MOL"^(-1), M_(B)=?` `M_(B)=(K_(f)xxW_(B))/(DeltaT_(f)xxW_(A))=((5.12" K kg mol"^(-1))xx(0.25 g))/((0.40 K)xx(0.024 kg ))=133.33" g mol"^(-1)`. |
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