The SI unit for molality is moles per kilogram of solvent. The SI unit for molality is mol/kg. A commonly used unit for molality in chemistry is mol/kg. In thermodynamics, the ebullioscopic constant relates molality to boiling point elevation. The deviations "tend" to become larger with increasing molality and temperature, but with some exceptions. "i" is the van 't Hoff factor, and "m" the molality.