How does Freezing Point Depression work

[jhanago]

I see that TF = Kf m i. Thus, the freezing point is depressed by adding NaCl for example. But, then why does it create a lower melting point and higher boiling point also?

It would seem that it makes more sense to have higher melting points if you have lower freezing

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[UBERlowGPA]

I see that TF = Kf m i. Thus, the freezing point is depressed by adding NaCl for example. But, then why does it create a lower melting point and higher boiling point also?

It would seem that it makes more sense to have higher melting points if you have lower freezing

melting point and freezing point should be at the same temp, therefore they would change in the same direction given the addition of ions. refer to an energy vs temp graph.

 

[predent9]

I see that TF = Kf m i. Thus, the freezing point is depressed by adding NaCl for example. But, then why does it create a lower melting point and higher boiling point also?

It would seem that it makes more sense to have higher melting points if you have lower freezing

Freezing point is equal to melting point. For example water freezes at zero degrees C, and also melts at zero degrees C. Adding ions to an aqueous solution disrupts the hydrogen bonds; they don’t fit into the crystal structure of ice, so they will require a lower temperature in order to be "fitted" into this structure - freezing point depression.

If you add ions to a solution, there is an increase in the intermolecular forces present. So in order to boil the new solution with added ions, it will require more energy (heat) to break these new intermolecular forces than the amount that was needed before adding the ions - boiling point elevation.