Question

0.90g of a non-electolyte was dissolved in 87.9 g of benzene. This reised the boiling point of benzene by `0.25^(@)C`. If the molecular mass of the non-electrolyte is 103.0 g `mol^(-1)` , calculate the molal elecation constant for benzene.

Answer 1

`K_(B)=(DeltaT_(b)xxM_(B)xxW_(A))/W_(B)`
`W_(B)=0.90g,W_(A)=87.9g=0.0879 kg, M_(B)=103.0 g mol^(-1),`
`DeltaT_(b)=0.25 K`
`K_(b)=((0.25K)xx(103.0gmol^(-1))xx(0.0879kg))/((0.90g))=2.52 K kg mol^(-1)`