I have been taught that if I have a solute of molality $m$ mixed with a liquid, the freezing point in lowered by an amount $K_\mathrm{f}\cdot m$ where $K_\mathrm{f}$ is the molal freezing depression constant.

But if I have a solution containing three liquids, and if all the $K_\mathrm{f}$ values are known, what would be the lowering of freezing point of such a solution?

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    $\begingroup$ At some point one of the liquids will reach its own freezing point lowered by presence of two other liquids and whatever else you have there. Then it will freeze. $\endgroup$ – Ivan Neretin Mar 26 at 13:31
  • $\begingroup$ How do we calculate the freezing point? $\endgroup$ – Vaishakh Sreekanth Menon Mar 26 at 13:42
  • $\begingroup$ Precisely as you described, via molality and Kf. $\endgroup$ – Ivan Neretin Mar 26 at 13:44
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    $\begingroup$ Sounds about right. $\endgroup$ – Ivan Neretin Mar 26 at 14:08
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    $\begingroup$ It is, not surprisingly, more complicated than that. The Kf*m model is an approximation to begin with, since it presume that Kf does not depend on concentration which is a poor approximation for many real liquids. But, an extension to a ternary would seem quite possible (and ternary interaction terms are not always needed). Depends on the liquids. $\endgroup$ – Jon Custer Mar 26 at 14:13

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