Answer to Question #159229 in Chemistry for Walid

Question

What is the boiling point elevation constant of urea

Answer 1

The boiling point elevation equation relates the change in boiling point of the solution compared to the solvent $\Delta T_b$ with the molality of the solution $m$ :

$\Delta T_b = iK_bm$ ,

where $i$ is the van't Hoff factor (equal to 1.0 for urea, as it doesn't associate nor dissociate) and $K_b$ is the ebullioscopic constant that depends on the properties of the solvent.

The urea is a white solid at standard temperature and pressure. Therefore, it usually acts as a solute and not a solvent. Therefore, the ebullioscopic constant in the equation is the constant for the solvent ( e.g. for the solutions in water (0.512 °C kg/mol) or in ethanol (1.23°C kg/mol)).