Final answer:
The elevation of boiling point method is used to determine the molecular weight of a non-volatile and soluble solute as the solute causes the solution's boiling point to be higher than that of the pure solvent.
Step-by-step explanation:
The elevation of boiling point method is used to determine the molecular weight of a non-volatile and soluble solute. When a nonvolatile solute is dissolved in a solvent, it causes the solution to have a higher boiling point than that of the pure solvent. This boiling point elevation occurs because the solute particles interfere with the evaporation of the solvent molecules, effectively reducing the solution's vapor pressure. In turn, the solution requires a greater temperature to reach the vapor pressure necessary for boiling.
The boiling point elevation (ΔT) is given by the equation ΔT = Kb × m, where Kb is the molal boiling-point elevation constant and m is the molality of the solution. For water, Kb equals 0.512°C/m. This method is useful for determining the molecular weight of a non-volatile solute because the elevation in boiling point is directly proportional to the molal concentration of the nonvolatile solute, which can be related to its molecular weight.