Editing Freezing-point depression (section)

===For dilute solution===
[[File:Tfreeze vs SA.png|thumb|237x237px|Freezing temperature of seawater at different pressures and some substances as a function of salinity. See image description for source.]]
If the solution is treated as an [[ideal solution]], the extent of freezing-point depression depends only on the solute concentration that can be estimated by a simple linear relationship with the cryoscopic constant ("[[Charles Blagden|Blagden]]'s Law").

:<math> \Delta T_f \propto \frac{\text{Moles of dissolved species}}{\text{Mass of solvent}}</math>

:<math> \Delta T_f = K_fbi</math>

where:
* <math>\Delta T_f</math> is the decrease in freezing point, defined as the freezing point <math> T_f^0</math> of the pure solvent minus the freezing point <math> T_f</math> of the solution, as the formula above results in a positive value given that all factors are positive. From the <math> \Delta T_f</math> calculated using the formula above, the freezing point of the solution can then be calculated as <math> T_f = T_f^0 - \Delta T_f</math>.
* <math>K_f</math>, the [[cryoscopic constant]], which is dependent on the properties of the solvent, not the solute. (Note: When conducting experiments, a higher ''k'' value makes it easier to observe larger drops in the freezing point.)
* <math>b</math> is the [[molality]] (moles of solute per kilogram of solvent)
* <math>i</math> is the [[van 't Hoff factor]] (number of ion particles per formula unit of solute, e.g. i = 2 for NaCl, 3 for BaCl<sub>2</sub>).

Some values of the cryoscopic constant ''K''<sub>f</sub> for selected solvents:<ref>{{cite book|first = P. W.|last = Atkins|title = Physical Chemistry|edition = 4th |page = C17 (Table 7.2)|isbn = 978-0716720737|publisher = Freeman|date = 1990}}</ref>

{| class="wikitable sortable"  
! Compound !! Freezing point (°C) !! ''K''<sub>f</sub> in [[kelvin|K]]⋅kg/[[mole (unit)|mol]]
|- 
| [[Acetic acid]] || 16.6 || 3.90
|- 
| [[Benzene]] || 5.5 || 5.12
|-
| [[Camphor]] || 179.8|| 39.7
|-
| [[Carbon disulfide]] || −112 || 3.8
|-
| [[Carbon tetrachloride]] || −23 || 30
|- 
| [[Chloroform]] || −63.5 || 4.68
|-  
| [[Cyclohexane]] ||  6.4  || 20.2
|-
| [[Ethanol]] || −114.6 || 1.99
|-
| [[Ethyl ether]] || −116.2 || 1.79
|-
| [[Naphthalene]] || 80.2 || 6.9
|-
| [[Phenol]] || 41 || 7.27
|-
| [[Water]] || 0 || 1.86<ref>{{Citation
  | last1 = Aylward
  | first1 = Gordon
  | author-link = Gordon Aylward
  | last2 = Findlay
  | first2 = Tristan
  | author2-link = Tristan Findlay
  | title = SI Chemical Data 5th ed.
  | place = Sweden
  | publisher = John Wiley & Sons
  | year = 2002
  | edition = 5
  | pages = 202
  | isbn = 0-470-80044-5}}</ref>
|}