elevation in boiling point

Figure explains elevation in boiling point when a non-volatile solute is added to a solvent. Variation of vapour pressure with temperaure and elevation in boiling point is marked. Given that DeltaT_(b) is the elevation in boiling point of the solvent in a solution of molarity m then lim_(m rarr 0) ((Delta T_(b))/(m)) is equal to:

Figure explains elevation in boiling point when a non-volatile solute is added to a solvent. Variation of vapour pressure with temperaure and elevation in boiling point is marked. Elevation in b.p of an aqueous urea solution is 0.52^(@) (K_(b) = 0.52^(@) mol^(-1)kg) . Hence, mole fraction of urea in this solution is:

The correct relation between elevation of boiling point and mass of solute is