Boiling Point Elevation and Concentration of Solute

The boiling point elevation is directly proportional to the molality of the solution. Thus,

where $m$ is the molality of the solution. The proportionality constant $K_b$ is called the boiling point elevation constant or molal elevation constant or ebullioscopic constant.

If $m = 1$, then $\Delta T_b = K_b$. Thus, the ebullioscopic constant is the boiling point elevation produced by a 1 molal solution.

Units of $K_b$ : $K_b = \dfrac{\Delta T_b}{m} = \dfrac{\mathrm{K}}{\mathrm{mol\,kg^{-1}}} = \mathrm{K\,kg\,mol^{-1}}$