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I am doing a research project that has to do with finding how efficient certain substances are at lowering the freezing point of water (freezing point depression) compared to other substances. So far, my research has showed that I can use the formula "ΔTF = KF · b · I" for ideal solutions. If the solution isn't ideal, then the ΔTF is altered from the standard calculation. What solutes can I mix with water that would result in an ideal or near-ideal solution?
Question Date: 2016-08-27
Answer 1:

I like your research project. It's not clear what the letters in your equation mean, though.

The equation I found is: ΔT = i Kf m

OK - it looks like maybe you used the equation in Wikipedia's article on freezing point depression. That explains the letters in the equation.


In general, dilute solutions in water are ideal solutions. Also, if the water gets hotter or colder when you add the solute, it's not an ideal solution.

Salt and sugar would be 2 nice solutes to add to water to measure freezing point depression. Salt separates into 2 ions in water, Na+ and Cl-, so a mole of salt should depress the freezing point of water twice as much as a mole of sugar, which has molecules, not ions.

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