Talk:Freezing-point depression

message: From the article:
ΔTf = i · Kf · activity
    * activity is in units of mol/kg, and is equal to an activity coefficient times the molality
...
    * i is the i factor or the van 't Hoff factor (see van 't Hoff), accounts for the number of individual ions formed by a compound in solution.
Eehm, isn't i the activity coefficient? I'm a bit puzzled, but it seems to me that it is used twice here.
—The preceding unsigned comment was added by 83.98.253.62 (talk) 09:05, 6 February 2007 (UTC)
replies: text: No, i isn't the activity factor, and neither the activity factor or the activity of the solute is really applicable in the case of colligative properties, where the solute plays the passive role of diluting the solvent (which is why molality is the relevant concentration measure). The standard phrase "concentration, or to be more precise activity..." does not apply to colligative properties! The article has now been changed to reflect this. The activity (or better, the chemical potential) of the solvent is another matter, but the ΔTf formula is the final stage in a derivation where the chemical potential has been expressed in those other terms on the right hand of the equation. Tomas e 20:59, 20 October 2007 (UTC)
thread_title: Mistake???

message: Anyone willing to compile a table of freezing point depression constants for a variety of solvents?  I can do it if no one else does, but right now I'm busy.Quaxmonster 23:23, 22 May 2006 (UTC)
replies: text: I compiled one from Atkins Physical Chemistry & German Wikipedia. Feel free to add more solvents! Tomas e 20:59, 20 October 2007 (UTC)

text: Thank you for pointing this out. I searched the article history and found that the table was deleted on 19 May 2010 (!) by a numbered user with no explanation. Normally such deletions are reverted quickly but not this time. I have now restored the original table. Dirac66 (talk) 13:03, 4 November 2020 (UTC)
thread_title:  Table of constants? 

message: I think it would be wise to include a section on what exactly causes freezing point depressions.  I would also be glad to add this section if there are no objections--Helgers7 05:57, 15 May 2007 (UTC)
replies: text: I've added a section on this, based on a diagram of chemical potential against temperature. It's correct, but it can probably be made more pedagogical. However, this is a phenomenon where I've often seen erroneous explanations (and I just removed one from the end of the previous version of the article). Many people are tempted to find "direct" molecular explanations, which tend to be nonsense in the case of colligative properties (and in many other cases where more subtle entropic phenomena are to be explained). Tomas e 20:59, 20 October 2007 (UTC)
replies: text: Why isn't it there, then??? 134.197.153.254 (talk) 19:54, 21 September 2010 (UTC)

text: And lo and behold someone did exactly that.  They did a Crystal Defect explanation which is utterly wrong.  We now have an article explaining this based on someone's intuition rather than fact.  Entropy is the only good description to be used here.  Crystal defect should be removed entirely. 66.114.154.25 (talk) 18:08, 17 April 2023 (UTC)
thread_title:  Theory 

message: I suggest to change the unit of temperature into kelvin.
Another suggestion to change the molality for molar fraction.
Both of them preferred by IUPAC documents for units and quantities.  Regards, --ZJ (talk) 13:42, 22 February 2010 (UTC)
thread_title:  unit of equations 

message: \Delta T_f= \frac{\Delta H^{fus}_{TF}-2R T_F \log{a_{liq}}-\sqrt{2\Delta C^{fus}_P T_F^2 R \log{a_{liq}} (\Delta H^{fus}_{TF})^2}}
{2(\Delta H^{fus}_{TF}/T_F+0.5\Delta C^{fus}_P - R \log{a_{liq}})}
I did not verify it being correct  —Preceding unsigned comment added by 130.237.74.66 (talk) 16:21, 8 December 2010 (UTC)
thread_title:  Math formula improvement 

message: The article claims the freezing point of pure water to be zero degree C. However the article Properties of Water states that in pure form it can be supercooled to -42 deg C.
I suggest that Pure Water in this article be exchanged with Ordinary Water or similar.  —Preceding unsigned comment added by 60.241.91.114 (talk) 07:19, 19 December 2010 (UTC)
thread_title:  Not so pure Pure Water 

message: This page needs a bit of a rewrite.  Using chemical potentials as an explanation is not an explanation at all.  It is simply making something needlessly more difficult so that the reader becomes too confused to question what is really going on beyond potentials.  Potentials are a result of what is happening, not the cause.  Molecules don't float around asking what their potential is before doing something.  Someone should put in a more appropriate entropic description!
Also, the line about (Explanations claiming that the solute molecules somehow "prevent" the solvent molecules from forming a solid are thus wrong.) is absolutely critical to this article, and should not be removed.  There are countless textbooks, instructors, and websites that use this INCORRECT explanation - and it should be addressed as it is totally false.  In fact the last entry in this discussion shows that junk like this was once present here.    —Preceding unsigned comment added by 168.156.39.231 (talk) 22:34, 9 January 2009 (UTC)
thread_title: Rewrite

message: Under "Uses" the section talks about adding salt to ice in order to cool beer. Would I be right in thinking that this is not about freezing point depression but due to enthalpy of fusion? Of course the freezing point of the ice is lowered but the actual temperature is lowered by the removal of heat to change the molecular arrangement of the water molecules. I'm not sure so I thought I'd ask before changing. Matthewcgirling (talk) 09:27, 11 February 2012 (UTC)
replies: text: Hmm, tricky. You're right, the cooling effect comes from the enthalpy of fusion. However, if there was no freezing point depression then there would be no melting and thus no cooling. --RolfSander (talk) 12:54, 11 February 2012 (UTC)
thread_title:  Enthalpy of Fusion? 

message: How is this concept of fpd applied to a mixture containing two electrolytes and water/solvent? Can the mixture of at least two electrolytes be considered a pseudo-component and the mixture thus a pseudo-binary mixture?--5.15.50.146 (talk) 11:44, 26 January 2016 (UTC)
replies: text: I don't really know what the definition of a pseudo-component is, but since freezing point depression basically depends on the dilution of the solvent and nothing else, summing up the dilution resulting from the various solutes should be correct. Tomas e (talk) 12:06, 28 February 2016 (UTC)
replies: text: It is defined at Apparent_molar_property#Multicomponent_mixtures_or_solutions--82.137.9.165 (talk) 20:28, 28 November 2017 (UTC)
thread_title:  Binary mixed electrolytes 

message: Explanations are garbage.  Solute prevents freezing?  Salt doesn't "fit" into the pure crystal?  Someone wrote this with no understanding of the subject.  Further there's been a lot of previous versions that mention enthalpy and cooling.  
The only viable explanation here is entropy and concentration.  Everything else needs to be nuked.  You can use chemical potential but that's already been discussed here as annoying. 
Use this: In the liquid solution, the solvent is diluted by the addition of a solute, so that fewer molecules are available to freeze. Re-establishment of equilibrium is achieved at a lower temperature at which the rate of freezing becomes equal to the rate of liquefying. At the lower freezing point, the vapor pressure of the liquid is equal to the vapor pressure of the corresponding solid, and the chemical potentials of the two phases are equal as well. 
66.114.154.25 (talk) 18:13, 17 April 2023 (UTC)
replies: text: Unfortunately, the word "entropy" does not occur at all in the subsection titled "Due to concentration and entropy". 73.50.103.119 (talk) 01:35, 23 August 2023 (UTC)
thread_title:  Garbage 

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thread_title:  A Commons file used on this page or its Wikidata item has been nominated for speedy deletion