**Unformatted text preview: **to yield (see the text above Eq. 5.119)
RT 2 M A
f
m or DT f = K f m B ,
DT f =
(5.119, 5.120)
D fus H m B
where Kf is called the cryoscopic constant of the solvent.
12 Boiling Point Elevation:
By considering the liquid-vapor equilibrium in which the vapor contains only the
component A, we can derive an expression analogous to that obtained above:
RT 2 M A
b
DT b =
m or DT b = K b m B
(5.126)
D vap H m B
where Kb is called the ebullioscopic constant of the solvent.
The elevation of boiling point is a rather weak effect compared to the depression
of freezing point. Therefore, the latter property is overwhelmingly used for the
practical applications of colligative properties.
Practical Applications:
Problems 5.39, 5.40, 5.46
These equations are useful to determine the freezing points or boiling points of
various solutions...

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