Boiling point elevation is the process in which adding a non-volatile solute to a solvent increases the boiling point of the solvent.
ΔTb = i .Kb. m
ΔTb = i .Kb.(w/M). (1000/W)
ΔTb – Boiling point elevation, i- Vant’ hoff factor, Kb – molal F.P. depression constant,
w- mass of the solute (g), M- Molar mass of Non-volatile solute, W- weight of solvent (g),
Calculate the elevation in boiling point when 13.5g of urea is dissolved in 260 g of water. Molal elevation constant of water is 0.52 K kg mole-1 and molecular mass of urea is 60g/mole.
Calculate the molality of the solution.
Moles of solute urea = 13.5g/60g/mole = 0.225 moles
molality = 0.225 moles/.260kg
Apply the boiling point elevation formula;
ΔTb = 1 x 0.52 x 0.225/.26 = 0.45K