Rajasthan BoardEnglish MediumSTD 12 ScienceChemistrySolutions2 Marks
Question
How to find out $K_b$ and $K_f$ ?
✓
Answer
$\begin{aligned} →\ \ K _f & =\frac{ R \times M _1 \times T_f^2}{1000 \times \Delta_{ Fus } H } \\ K _{ b } & =\frac{ R \times M _1 \times T_{ b }^2}{1000 \times \Delta_{\text {vap }} H }\end{aligned}$ $\begin{aligned}Where\ \ \ R & =\text { gas constant } \\ M _1 & =\text { Molar mass of solvent } \\ T_f & =\text { Freezing point of pure solvent } \\ T_{ b } & =\text { Boiling point of pure solvent. } \\ \Delta_{\text {Fus }}^{ H } & =\text { Fusion enthalpy } \\ \Delta_{\text {vap }}^{ H } & =\text { Vapourisation enthalpy }\end{aligned}$
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